CHAPTERS BOOKLET-4

Transcription

1 EMISTRY XII APTERS 1-1 BKLET-

2 ontents: Page No. hapter 1 Aldehydes and Ketones Part hapter 1 Aldehydes and Ketones Part 00-0 hapter 17 Aldehydes and Ketones Part 1- hapter 18 arboxyli Aids and their derivatives Part hapter 19 arboxyli Aids and their derivatives Part 9-80 hapter 0 arboxyli Aids and their derivatives Part 81-8 hapter 1 arboxyli Aids and their derivatives Part 8-0

3 Aldehydes and Ketones Part 1 Introdution. arbonyl ompounds are of two types, aldehydes and ketones. Both have a arbon-oxygen double bond often alled as arbonyl group. Both aldehyde and ketones possess the same general formula Aldehyde Aldehydes may be onsidered as derivatives of hydroarbons in whih two hydrogen atoms of the end arbon atom have been replaed by a bivalent oxygen atom. = Methane [ ] Formaldehyde Aldehydes ontain the monovalent group = (aldehydi group) linked to a hydrogen atom or an alkyl group. ene, the general formula of the aldehydes is represented as, R = (R may be or alkyl group). Aldehydes an also be regarded as the first oxidation produts of primary alohols. [ ] R R Primary alohol Aldehyde lassifiation, Struture, Nomenlature and Isomerism. (1) lassifiation Aldehydi group is always terminal. Aldehydes an be lassified into three ategories, (i) Aliphati aldehydes : R (ii) Aromati aldehydes : Ar (iii) Unsymmetrial aldehydes : All aldehydes exept formaldehyde are unsymmetrial. Formaldehyde R Both substituents are different Ketones ontain the divalent group n n. Ketone Ketones may be onsidered as derivatives of hydroarbons in whih the two hydrogen atoms of a arbon atom present in the middle of arbon hain have been replaed by a bivalent oxygen atom. Propane [ ] Aetone = (ketoni group) linked to two alkyl groups, same or different. ene, the general formula of the ketones is represented as, R = or R = R R' Ketones an also be regarded as the first oxidation produts of seondary alohols. Isopropyl alohol [ ] Aetone = Ketoni group is never terminal. Ketones an be lassified into three ategories, (i) Aliphati ketones : R R Symmetrial R R' Unsymmetrial (iii) Mixed ketones : In mixed ketones one substituent is aryl and other is alkyl. () Struture : arbonyl arbon atom is joined to three atoms by sigma bonds. Sine these bonds utilise sp -orbitals, they lie in the same plane and are 10 apart. The arbon-oxygen double bond is different than arbon-arbon double bond. Sine, xygen is more eletronegative, the eletrons of the bond are attrated towards oxygen. onsequently, oxygen attains a partial negative harge and arbon a partial arbonyl group (ii) Aromati ketones : In aromati ketones both substituents are aryl, Aryl group Alkyl group σ-bond π-bond hapter 1 8

4 Aldehydes and Ketones Part 1 positive harge making the bond polar. The high values of dipole moment, (. -.8D) annot be explained only on the basis of indutive effet and thus, it is proposed that arbonyl group is a resonane hybrid of the following two strutures. orresponding aid whih they form on oxidation. The suffix i aid the name of the aid is replaed by aldehyde. δ = δ = () Nomenlature (i) Aldehyde : There are two systems of naming aldehydes, (a) ommon system : In the ommon system, aldehydes are named aording to the name of the For example, Aeti aid derived from aeti aid ( ) is named as aetaldehyde. i aid aldehyde Aetaldehyde = Aeti aid aldehyde = aetaldehyde Branhing in the aldehyde hain, if any, is indiated by the Greek letters α, β, γ, δ et. The arbon attahed to the group is α as : γ β α For example, αmethyl butyraldehyde (b) IUPA system : In the IUPA system, the aldehydes are known as alkanals. The name of aldehyde is derived by replaing the terminal e of the name of orresponding alkane by al. For example, Alkane e al = Alkanal Methanal Ethanal Propanal (ii) Ketone : There are two systems of naming ketone, (a) ommon system : In the ommon system, ketones are named by using the names of alkyl group present in the moleule. For example, Dimethyl ketone Methyl npropylketone Ethyl methyl ketone () Methyl isopropyl ketone Diethyl ketone Benzyl methyl ketone Some of the ketones are known by their old popular names as well. For example, dimethyl ketone, is still popularly known as aetone. (b) IUPA system : In this system, longest hain ontaining the ketoni group is taken as the parent hain. In naming the ketone orresponding to the hain, the following proedure is adopted. Root word ane e one i.e., Alkanone The positions of the ketoni group and the substituents are indiated by the loants. Propanone Butanone- Pantanone- -Methylhexanone- () Isomerism : Aldehydes show hain and funtional isomerism. hain isomers : nbutanal ( ) -Methylpropanal ( isobutanal) hapter 1 8

5 Aldehydes and Ketones Part 1 (i) Funtional isomers: ; ; = ; ; =.. Propanal Aetone Allyl alohol α, β Propylene oxide Note: When the seondary alohols an be oxidised to ketones by aluminium tert-butoxide, Methyl vinyl ether Ketones show hain, funtional and metamerism. Examples of funtional isomerism is given above in aldehydes. (ii) hain isomers : (iii) Metamers : Methylpropyl ketone Methylpropyl ketone ; ; Preparation of arbonyl ompounds. ( ) Methylisopropyl ketone Diethyl ketone Preparation of only aliphati or aliphati as well as aromati arbonyl ompounds. (1) From alohols (i) Primary and seondary alohols on oxidation give aldehydes and ketones respetively. Mild oxidising R R' R R' agents Mild oxidising R R Mild oxidising agents are : agents (a) X (b) Fenton reagent () (e) Sarret reagent (f) Mn K r7 / (d) Jones reagent (g) Aluminium tertiary butoxide [( ) ] Al the reation is known as oppenauer oxidation. Unsaturated seondary alohols an also be oxidised to unsaturated ketones (without affeting double bond) by this reagent. The yield of aldehydes is usually low by this methods. The alohols an be onverted to aldehydes stage by treating with oxidising agent pyridinium hloro-hromate ( N rl ). It is abbreviated as P and is alled ollin's reagent. This reagent is used in non-aqueous solvents like l (dihloro methane). It is prepared by mixing pyridine, r and l in dihloromethane. This is a very good reagent beause it heks the further oxidation of aldehydes to arboxyli aids. (ii) Dehydrogenation of 1 and alohols by u/00 or Ag/00. u / 00 R R u / 00 R R' R R' () From arboxyli aids (i) Distillation of a, Ba, Sr or Th salts of monobasi aids: Salt of monobasi aids on distillation give arbonyl ompounds. Reation takes plae as follows, hapter 1 8

6 Aldehydes and Ketones Part 1 a ( R' ) a R R' ( R ) a Thus in the produt, one alkyl group omes from one arboxyli aid and other alkyl group from other arboxyli aid. (ii) atalyti deomposition of arboxyli aids or Dearboxylation and Dehydration of aids by Mn/ 00. ( ) a ( a ) ( R) a ( a R ) (Equimolar amount) ' (Equimolar amount) ( R) a ( R) a R R ( ) a ( a ) ( a ) a ( ) alium salts of dibasi aid (1, and higher) on distillation give yli ketones. a Distillation ( ) a Distillation (a) This reation takes plae between two moleules of arboxyli aids. Both may be the same or different. (b) If one of the arboxyli aids is then this aid undergoes dearboxylation beause this aid is the only monobasi aid whih undergoes dearboxylation even in the absene of atalyst. ase I : When both are ase II : When only one is formi aid. R ase III : When none is formi aid. R R Mn 00 Mn / 00 R Mn / 00 ylopropanone ylohexanone R R hapter 1 87

7 Aldehydes and Ketones Part 1 R R' R R' r Mn / 00 () From gem dihalides : Gem dihalides on hydrolysis give arbonyl ompounds Note : This method is not used muh sine aldehydes are affeted by alkali and dihalides are usually (i) (ii) R X X / R / R R' R R' X () From alkenes prepared from the arbonyl ompounds. (i) zonolysis : Alkenes on redutive ozonolysis give arbonyl ompounds (i) R = R R R (ii) / Zn R R = R' (i) R R R' R' (ii) / Zn R' Note : This method is used only for aliphati arbonyl ompounds. (ii) xo proess : This method onverts terminal alkenes into aldehydes. ( ) R = R 8 10, 00 atm Note : xo proess is used only for the preparation of aldehydes. (iii) Waker proess : This reation onverts alkenes in arbonyl ompounds. (a) Pdl / = air / ul (b) R = R Pdl / air/u l () From alkynes : Alkynes on hydration and on boration oxidation give arbonyl ompounds. R /gs / S (i) Sia B (ii) / R R () From Grignard reagents : arbonyl ompounds an be prepared from Grignard reagents by following reations: hapter 1 88

8 Aldehydes and Ketones Part 1 R' l R' R R (nly ketone) (Aldehyde) R MgX (Exess) (7) From aid hloride (i) Aid hlorides give nuleophili substitution reation with dialkyl admium and dialkyl lithium uprate to give ketones. This is one of the most important method for the preparation of ketones from aid hlorides. R l R' d R R' R' uli R' (i) N (ii) / (i) R' N (ii) / = R l R R' (nly used for the preparation of ketones) R R' R R R' R (Ketone) In this method produt is always ketone beause R and also R'. (ii) Rosenmunds redution : Aid hlorides on partial redution give aldehydes. This redution takes plae in the presene of Lindlars atalyst. / PdBaS a R l R Xylene / PdBaS a Ar l Ar Xylene (nly used for aldehydes) (8) From yanides hapter 1 89

9 Aldehydes and Ketones Part 1 (i) Stephen aldehyde synthesis : onversion of yanides into aldehydes by partial redution with Snl / l, followed by hydrolysis, is known as Stephens aldehyde synthesis. Example : (i) Snl / l / ether R N R (nly used for aldehydes) (ii) / or steam distillation (10) From Alkyl halides and benzyl halides : These ompounds on oxidation give arbonyl ompounds. (i) Snl / l (ii) / (i) Snl / l (ii) / (9) From vi diols : Vi diols on periodate oxidation give arbonyl ompounds. I R R R R R Note : Pb( ) also gives similar oxidation produts. l DMS DMS R l R ; R R R R DMS or (i) ( ) N l ( ii) / or u( N ) or Pb( N ) R (11) From nitro alkanes : Nitro alkanes having at least one α -hydrogen atom give arbonyl ompounds on treatment with on Na followed by 70% S. The reation is known as Nef arbonyl synthesis. R N Na R = N 70% S R N ylopentane nitrile N Benzenenitrile Tautomerisation ylopentanaldehyde Benzaldehyde R R N (i) Na R R (ii) S (1) Reation with exess alkyl lithium : arboxyli aids reat with exess of organo lithium to give lithium salt of gem diols whih on hydrolysis give ketones. R' (i) RLi (exess) R' R (ii) / Preparation of only aromati arbonyl ompounds hapter 1 90

10 Aldehydes and Ketones Part 1 (1) From methyl arenes : Methyl (i) arenes r l an be onverted into aldehydes by the following reagents (ii) (i) r /( ) / (ii) Air/Mn () From hloro methyl arenes : hloromethyl arenes on oxidation give aromati aldehydes. l 00 u(n ) / Pb(N ) / (i) ( ) N / (ii) () Gattermann Koh formylation : This reation is mainly given by aromati hydroarbons and halobenzenes. l /l /Anhy. Znl /l /Anhy. Znl /l /Anhy. Znl () Gattermann formylation : This reation is mainly given by alkyl benzenes, phenols and phenoli ethers. l l (i) Zn(N) /l gas (ii) / (i) Zn(N) /l gas (ii) / (i) Zn(N) /l gas (ii) / hapter 1 91

11 Aldehydes and Ketones Part 1 () ouben oesh reation : This reation is given by di and polyhydri benzenes. (i) RN/l gas/anhy.znl (ii) R () Reimer Tiemann reation : Phenol gives 0- and p- hydroxy benzaldehyde in this reation. (i) RN/l gas/anhy.znl (ii) (i) l /Al.K/ (ii) / Physial properties of arbonyl ompounds. R The important physial properties of aldehydes and ketones are given below, (1) Physial state : Methanal is a pungent smell gas. Ethanal is a volatile liquid, b.p. 9 K. ther aldehydes and ketones ontaining up to eleven arbon atoms are olourless liquids while still higher members are solids. () Smell : With the exeption of lower aldehydes whih have unpleasant odours, aldehydes and ketones have generally pleasant smell. As the size of the moleule inreases, the odour beomes less pungent and more fragrant. In fat, many naturally ourring aldehydes and ketones have been used in blending of perfumes and flavouring agents. () Solubility : Aldehydes and ketones upto four arbon atoms are misible with water. This is due to the presene of hydrogen bonding between the polar arbonyl group and water moleules as shown below : δ δ δ δ δ δ = δ With the inrease in the size of alkyl group, the solubility dereases and the ompounds with more than four arbon atom are pratially insoluble in water. All aldehydes and ketones are, however, soluble in organi solvents suh as ether, alohol, et. The ketones are good solvents themselves. () Boiling points : The boiling points of aldehydes and ketones are higher than those of non polar ompounds (hydroarbons) or weakly polar ompounds (suh as ethers) of omparable moleular masses. owever, their boiling points are lower than those of orresponding alohols or arboxyli aids. This is beause aldehydes and ketones are polar ompounds having suffiient intermoleular dipole-dipole interations between the opposite ends of = dipoles. hapter 1 9

12 Aldehydes and Ketones Part 1 δ = δ δ = δ δ = δ owever, these dipole-dipole interations are weaker than the intermoleular hydrogen bonding in alohols and arboxyli aids. Therefore, boiling points of aldehydes and ketones are relatively lower than the alohols and arboxyli aids of omparable moleular masses. ompounds Pentane Ethoxyethane Butan - 1-ol Butanal Butan--one Moleular mass Boiling point (K) Among the arbonyl ompounds, ketones have slightly higher boiling points than the isomeri aldehydes. This is due t0.o the presene of two eletrons releasing groups around the arbonyl arbon, whih makes them more polar. = : Aetaldehyde µ =.D b.pt. = K.. Aetone µ =.88 D b.pt= 9 K.. = : () Density : Density of aldehydes and ketones is less than that of water. hemial properties of arbonyl ompounds. arbonyl ompounds give hemial reations due to arbonyl ompounds group and α-hydrogens. hemial reations of arbonyl ompounds an be lassified into following ategories. (1) Nuleophili addition reations () Addition followed by elimination reations () xidation () Redution () Reations due to α-hydrogen () ondensation reations and (7) Misellaneous reations (1) Nuleophili addition reations (i) arbonyl ompounds give nuleophili addition reation with those reagents whih on dissoiation give eletrophile as well as nuleophile. (ii) If nuleophile is weak then addition reation is arried out in the presene of aid as atalyst. (iii) Produt of addition reations an be written as follows, δ δ δ Addition R R' Nu δ R R' Nu Addut In addition reations nuleophile adds on arbonyl arbon and eletrophile on arbonyl oxygen to give addut. (iv) Relative reativity of aldehydes and ketones : Aldehydes and ketones readily undergo nuleophili addition reations. owever, ketones are less reative than aldehydes. This is due to eletroni and steari effets as explained below: hapter 1 9

13 Aldehydes and Ketones Part 1 (a) Indutive effet : The relative reativities of aldehydes and ketones in nuleophili addition reations may be attributed to the amount of positive harge on the arbon. A greater positive harge means a higher reativity. If the positive harge is dispersed throughout the moleule, the arbonyl ompound beomes more stable and its reativity dereases. Now, alkyl group is an eletron releasing group (I indutive effet). Therefore, eletron releasing power of two alkyl groups in ketones is more than that of one in aldehyde. As a result, the eletron defiieny of arbon atom in the arbonyl group is satisfied more in ketones than in aldehydes. Therefore, the redued positive harge on arbon in ase of ketones disourages the attak of nuleophiles. ene ketones are less reative than aldehydes. Formaldehyde with no alkyl groups is the most reative of the aldehydes and ketones. Thus, the order of reativity is: = > Formaldehyde R = > Aldehyde R R = (b) Steari effet : The size of the alkyl group is more than that of hydrogen. In aldehydes, there is one alkyl group but in ketones, there are two alkyl groups attahed to the arbonyl group. The alkyl groups are larger than a hydrogen atom and these ause hindrane to the attaking group. This is alled steari hindrane. As the number and size of the alkyl groups inrease, the hindrane to the attak of nuleophile also inreases and reativity dereases. The lak of hindrane in nuleophili attak is another reason for the greater reativity of formaldehyde. Thus, the reativity follows the order: = > Formaldehyde Aetaldehyde = > Aetone = > ( ( Ketone ) ) Di -isopropyl ketone = > butyl ketone ( ( ) ) Di-tert. = In general, aromati aldehydes and ketones are less reative than the orresponding aliphati analogues. For example, benzaldehyde is less reative than aliphati aldehydes. This an be easily understood from the resonating strutures of benzaldehyde as shown below:.. :.... :.... :.... : I II III IV V It is lear from the resonating strutures that due to eletron releasing (I effet) of the benzene ring, the magnitude of the positive harge on the arbonyl group dereases and onsequently it beomes less suseptible to the nuleophili attak. Thus, aromati aldehydes and ketones are less reative than the orresponding aliphati aldehyde and ketones. The order of reativity of aromati aldehydes and ketones is, > Benzaldehyde > Aetophenone Benzophenone Some important examples of nuleophili addition reations Some important nuleophili addition reations of aldehydes and ketones are given below, hapter 1 9

14 Aldehydes and Ketones Part 1 Addition of N : arbonyl ompounds reat with N to form yanohydrins. This reation is atalysed by base. R N R N Note : Beause N is a toxi gas, the best way to arry out this reation, to generate hydrogen yanide yanohydrin N N during the reation by adding l to a mixture of the arbonyl ompound and exess of NaN. Benzophenone does not reat with N. Exept formaldehyde, all other aldehydes gives optially ative yanohydrin (raemi mixture). This reation is synthetially useful reation for the preparation of α-hydroxy aids, β-amino alohols and α- hydroxy aldehydes. R N R R R α-ydroxy aid N (If R is then produt is lati aid). β -Amino alohol Addition of sodium bisulphite : Sodium bisulphite dissoiates as follows: NaS S Na Eletrophile // /Pt (i) Snl /l (ii) / Nuleophile (i) All types of aldehydes give addition reation with this reagent. The addut of aldehyde is white rystalline ompound whih again onverts into aldehyde on treatment with aid, base or. S Na or or R R R S Na rystallin Addut; white e in nature (ii) nly aliphati methyl ketones give addition reation with sodium bisulphite. S Na or or R R R S Na olourless rystalline produt Note : This reagent an be used for differentiation between ketones and aliphati methyl ketones, e.g. hapter 1 9

15 Aldehydes and Ketones Part 1 and and These two ompounds an be separated from their mixture by the use of NaS. igher aliphati This reagent an be used for the separation of aldehydes and aliphati methyl ketones from the mixture, e.g. and ketones and aromati ketones do not reat with NaS. Addition of alohols : arbonyl ompounds give addition reation with alohols. This reation is atalysed by aid and base. Nature of produt depends on the atalyst. ase I : Addition atalysed by base : In the presene of base one equivalent of an alohol reats with only one equivalent of the arbonyl ompound. The produt is alled hemiaetal (in ase of aldehyde) and hemiketal (in ase of ketone). The reation is reversible. There is always equilibrium between reatants and produt. δ δ emiaetal emiaetals and hemiketals are α-alkoxy alohols. emiketal ase II : Addition atalysed by aid : In the presene of aid one equivalent of arbonyl ompound reats with two equivalents of alohol. Produt of the reation is aetal (in ase of aldehyde) or ketal (in ase of ketone). R R R R Aetal R R Ketal (i) Formation of aetals and ketals an be shown as follows: hapter 1 9

16 Aldehydes and Ketones Part 1 R R R = R (ii) Aetals and ketals are gem dialkoxy ompounds. (iii) igh yield of aetals or ketals are obtained if the water eliminated from the reation is removed as it formed beause the reation is reversible. (iv) Aetals and ketals an be transformed bak to orresponding aldehyde or ketone in the presene of exess of water. R R R R Ketal (Exess) This reation is very useful reation for the protetion of arbonyl group whih an be deproteted by hydrolysis. Glyol is used for this purpose. Suppose we want to arry out the given onversion by LiAl. LiAl This an be ahieved by protetion of LiAl = group and then by deprotetion / Protetion / Addition of Grignard reagents : Grignard reagents reat with arbonyl ompounds to give alohols. Nature of alohol depends on the nature of arbonyl ompound. (i) (ii) / R 1 -alohol RMgX (i) R' (ii) / R' R -alohol (i) R' R' R' R' -alohol (ii) / R Addition of water : arbonyl ompounds reat with water to give gem diols. This reation is atalysed by aid. The reation is reversible reation. hapter 1 97

17 Aldehydes and Ketones Part 1 R R' R R' Gem diols are highly unstable ompounds hene equilibrium favours the bakward diretion. The extent to whih an aldehyde or ketone is hydrated depends on the stability of gem diol. (i) Steri hindrane by I group around α-arbon dereases the stability of gem diols. I group dereases Stability of gem diols depend on the following fators: stability of gem diol and hene dereases extent of hydration. 0.1% % 99.8% 99.9% 8% 0.% (ii) Stability of gem diols mainly depends on the presene of I group on α-arbon. More is the I power of the group more will be stability of gem diols. F F l l F F F F These gem diols are highly stable due to the presene of I group on α-arbon. (iii) Intramoleular hydrogen bonding inreases stability of gem diols. I groups present on arbon having gem diol group inreases strength of hydrogen bond. (i) I power of I group is in inreasing order (ii) Stability in dereasing order hapter 1 98

18 Aldehydes and Ketones Part 1 Strength of hydrogen bond α I power of the group. More is the strength of hydrogen bond more will be the stability of gem diol. Addition of terminal alkynes : Sodium salt of terminal alkynes reat with arbonyl ompounds to give alkynol. This reation is known as ethinylation. () Addition followed by elimination reations : This reation is given by ammonia derivatives R Na R' R R Some examples are, ( N Z). (i) N a (ii) / (i) N a N a (ii) / N a / R" R R" R' R' (i) (ii) / (i) In nuleophili addition reations poor nuleophile suh as ammonia and ammonia derivatives requires aid as atalyst. (ii) If the attaking atom of the nuleophile has a lone pair of eletrons in the addition produt, water will be eliminated from the addition produt. This is alled a nuleophili addition elimination. Primary amines and derivatives of ammonia reat with arbonyl ompounds to give addut. In addut nuleophili group has lone pair of eletrons. It undergoes elimination to give produt known as imine. An imine is a ompound with a arbon-nitrogen double bond. δ δ.. R R N Z R R N Z.. The overall reation an be shown as follows: R R = N Z An imine R R.. = N R Z R = N R An imine hapter 1 99

19 Aldehydes and Ketones Part Different imine formation with N Z is given below R' N // R = N R' R Imine from p-amine (Shiff base) N // R R = N xime Ketoxime when treated with aid at 0 it undergoes rearrangement known as Bekmann rearrangement. Thus aid atalysed onversion of ketoximes to N-substituted amides is alled Bekmann rearrangement. Aid atalyst used are proton aids ( S, l, P ) and Lewis aids ( Pl, Sl, PhSl, Rl, S, BF et.) R R N N N (i) Pl (ii) (i) Pl N N // N N / N N (ii) N In short produt of the rearrangement an be obtained as follows: R R' R' R' N R N RN () xidation of arbonyl ompounds N N N N // Semiarbazide N // Tautomerisation hapter 1 00 R R R R R = N N ydrazone = N NN Phenylhydrozone (Brown oloured) = N N R,-Dinitrophenylhydrazone (Red oloured) R R N = N N N Semiarbazone N

20 Aldehydes and Ketones Part (i) xidation by mild oxidising agents : Mild oxidising agents oxidise only aldehydes into arboxyli aids. They do not oxidises ketones. Main oxidising agents are: (a) Fehling solution : It is a mixture of two Fehling solution: Fehling solution No.1 : It ontains us solution and Na. Fehling solution No. : It ontains sodium potassium tartrate. (Roshelle salt). (b) Benedit's solution : This solution ontains us, Na Reating speies of both solutions is and sodium or potassium itrate. u oxidation no. of u varies from to 1. These two oxidising agents oxidise only aliphati aldehydes and have no effet on any other funtional groups: Redox u u (as u ) (red ppt.) reation u = = u u ) ( ) ( u Benedit's solution and Fehling solutions are used as a reagent for the test of sugar (gluose) in blood sample. () Tollens reagent : Tollens reagent is ammonial silver nitrate solution. Its reating speies is It oxidises aliphati as well as aromati aldehydes. R Ag Redox R Ag (as silver mirror) reation Ag Ag This reagent has no effet on arbon-arbon multiple bond. = Ag = Ag = Ag = Ag In this reation the oxidation no. of Ag varies from 1 to 0. Note : Gluose, frutose give positive test with Tollen's reagents and Fehling solution. 11 u (or) Ag Frutose ontain 11 Gluoni aid Ag. = (keto) group yet give positive test with Fehling solution due to presene of hydroxyl group. Tollens reagent also gives positive test with terminal alkynes and. Reation with meruri hloride solution : R gl R l g l (White) ( ) R g l R l g( ) (Blak) Shiff's reagent : Megenta dye S olourless soln pink olour restored. hapter 1 01

21 Aldehydes and Ketones Part (ii) xidation by strong oxidising agents : Main strong oxidising agents are KMn / /, KMn / /, K r7 / well as ketones. / and on (a) xidation of aldehydes : Aldehydes are oxidised into orresponding aids. R = n [ R ; ] = n KMn / / N /. These agents oxidise aldehydes as (b) xidation of ketones : Ketones undergo oxidation only in drasti onditions. During the oxidation of ketones there is breaking of arbon-arbon bond between α-arbon and arbonyl arbon. In this proess both arbons onvert into arboxyli groups. This leads to the formation of two moles of monoarboxyli aids. ase I : xidation of symmetrial ketones α = 7 [ ] = Total number of 'S= = Thus number of arbons in any produt is less than the number of arbons in ketone. 7 = ase II : xidation of unsymmetrial ketones : In ase of unsymmetrial ketones α-arbon whose bond breaks always belongs to the alkyl group whih has more number of arbons. This rule is known as Poff s rule. [ ] ase III : xidation of yli ketones : Formation of dibasi aid takes plae from yli ketones. In this ase number of arbons in ketone and dibasi arboxyli aid is always same. α [ ] ( ) Note : If both α-arbons are not idential then bond breaking takes plae between arbonyl arbon and α-arbon whih has maximum number of hydrogens. α 1 [ ] ( ) (iii) Misellaneous oxidation (a) aloform Reation : In this reation α-methyl arbonyl ompounds undergo oxidation with (i) X / R R X (ii) X /. hapter 1 0

22 Aldehydes and Ketones Part (i) X / (i) I (ii) / Na (ii) X I (b) xidation at α- or by Se : Se oxidises α group into aldehydi group. α In this oxidation reativity of is more than the group and xidation is regio seletive in nature. Se ; Glyoxal Se Dimethylglyoxal Se Methylglyoxal group into keto group and () xidation by organi peraids : rgani peraids oxidise aldehydes into arboxyli aids and ketones into esters. This oxidation is known as Baeyer Villiger oxidation. R R ; R R R In ase of aldehyde there is insertion of atomi oxygen (obtained from peraid) between arbonyl arbon and hydrogen of arbonyl arbon. In ase of ketone, insertion of oxygen takes plae between arbonyl arbon and α-arbon. Thus the produt is ester. This is one of the most important reation for the onversion of ketones into esters. Symmetrial ketones : F ε-latone Unsymmetrial ketones : In ase of unsymmetrial ketones preferene of insertion in dereasing order is as > R > R > Ph > 1 R > F F Se hapter 1 0

23 Aldehydes and Ketones Part Note : Vi diarbonyl ompound also undergo oxidation & produt is anhydride. R R R R Popoff's rule : xidation of unsymmetrial ketones largely take plae in suh a way that the smaller alkyl group remains attahed to the group during the formation of two moleules of aids. This is known as Popoff's rule group into group : Following three reagents redue arbonyl group into Example : (d) Baeyer- villiger oxidation : Note : Reation will be held if the oxidation agent is performi aid. groups: (a) I / P / (b) Zn / g / on. l and () () Reution of arbonyl ompounds (i) Redution of R R' [ ] N N /. R R' (ii) Redution of arbonyl ompounds into hydroxy ompounds : arbonyl group onverts into group by LiAl, NaB, Na / and aluminium isopropoxide. (i) LiAl (i) LiAl R R ; R R' R R' (ii) NaB (iii) Aluminium isopropoxide (ii) NaB (iii) Aluminium isopropoxide NaB is regioseletive reduing agent beause it redued only. in the presene of other reduible group. NaB I/P/ Zn/g/on. l Example : = = ydride ion of NaB attak on arbonyl arbon during redution. NaBD D D NaBD Example : -Butanone D D D NaB D N N / hapter 1 0 R R' R R' (lemmensen redution)

24 Aldehydes and Ketones Part (iii) Redutive amination : In this redution R R = N R R (i) N (ii) Im ine group onverts into N group as follows: R / Ni = N N R / Ni N Primary -amine, the produt is vi trans diol. (iv) Redution of ketones by Mg or Mg/g : In this ase ketones undergo redution via oupling reation and produt is vi is diol. R R (i) Mg / g R R R (ii) R R R Vi is diol When this reation is arried out in the presene of Mg / g / Til (i) g Mg Til (ii) (v) Redution of benzaldehyde by Na/ : Benzaldehyde undergoes redution via oupling reation and produt is vi diol. (i) Na/ (ii) (Bouveault-blan reation) vi diol Note : Aldehydes are redued to 1 alohols whereas ketones to alohols. If arbon arbon double bond is also present in the arbonyl ompound, it is also redued alongwith. owever, the use of the reagent 9-BBN (9 borabiylo (,, 1) nonane) prevents this and thus only the arbonyl group is redued Example : Vi trans diol 9 N BBN = = innamaldehyde innamyl alohol If reduing agent is Na, reation is alled Darzen's reation, we an also use LiAl in this reation. If reduing agent is aluminium iso propoxide ( ) Al. Produt will be alohol. This reation is alled Meerwein pondorff verley redution (MPV redution). The perentage yield of alkanes an be inreased by using diethylene glyol in Wolf Kishner redution. Then reation is alled uang Millan onversion. (vi) ydrazones when treated with base like alkoxide give hydroarbon (Wolf Kishner redution). N. N NN RNa R R' R R' R R ydrazone hapter 1 0

25 Aldehydes and Ketones Part (vii) Shiff's base on redution gives seondary amines. R N ' / Ni R = R = NR ' R Shiff's base () Reations due to α-hydrogen (i) Aidity of α-hydrogens : NR (a) α-hydrogen of arbonyl ompounds are aidi in harater due to the presene of the eletron withdrawing group. (b) Thus arbonyl ompounds having α-hydrogen onvert into arbanions in the presene of base. This arbanion is stabilised by deloalisation of negative harge. R R (more Enolate = R arbanion (less stable) stable) ion () The aidity of α-hydrogen is more than ethyne. pka value of aldehydes and ketones are generally 19 0 where as pka value of ethyne is. (d) ompounds having ative methylene or methyne group are even more aidi than simple aldehydes and ketones. pka = 1. 9 ; pka = 8. (ii) alogenation : arbonyl ompounds having α-hydrogens undergo halogenation reations. This reation is atalysed by aid as well as base. (a) Aid atalysed halogenation : This gives only monohalo derivative. α-arbon Br / (b) Base atalysed halogenation : In the presene of base all α-hydrogens of the same arbon is replaed by halogens. Base X / (Exess) X / X X α-ydrogen is aidi due to strong I group;. Br X X hapter 1 0

26 Aldehydes and Ketones Part arbonyl ompounds having three α-hydrogens give haloform reation. R X / R X R X (iii) Deuterium exhange reation : Deuterium exhange reation is atalysed by aid ) ( D ). In both the ases all the hydrogens on only one α-arbon is replaed by D. as base. D / D R R R D D / D R ; R R R D R ( D as well as base (iv) Raemisation : Ketones whose α-arbon is hiral undergo Raemisation in the presene of aid as well or Raemi mixture (v) Alkylation : arbonyl ompounds having α-hydrogens undergo alkylation reation with RX in the presene of base. This reation is SN reation. The best result is obtained with elimination in the presene of strong base. Na (Small base) I (Main produt) I X. ther halides undergo (Main produt) (vi) Wittig reation : Aldehyde and ketones undergo the wittig reation to form alkenes. 1 Ph P = R R Ph P R Ph P R Ph P R R 1 R () ondensation reation of arbonyl ompounds : Nuleophili addition reation of ompounds having arbonyl group with those ompounds whih have at least one aidi hydrogen at α-arbon is known as ondensation reation. In this addition reation : Substrate is always an organi ompound having a arbonyl group, e.g. LDA (Bulky base),, R, Addition always takes plae on the arbonyl group. R R et. 1 R 1 hapter 1 07

27 Aldehydes and Ketones Part Reagents of the ondensation reation are also organi ompounds having at least one hydrogen on α-arbon and α-arbon should have I group, e.g. α α α N,, N Note : If substrate and reagent both are arbonyl ompounds then one should have at least one α- hydrogen and other may or may not have α-hydrogen. ondensation reation always takes plae in the presene of aid or base as atalyst. Best result is obtained with base at lower temp. R R or Z R Z R ondensation is arried out at lower temperature ( 0 ) has strong I group at β-arbon. R Z α β beause produt of the reation is alohol whih R Suh type of alohols are highly reative for dehydration. They undergo dehydration in the presene of aid as well as base even at. They also undergo elimination even on strong heating. R / R Z = Z α β Dehydration R R (i) Aldol ondensation (a) This reation takes plae between two moleules of arbonyl ompounds; one moleule should have at least two α-hydrogen atoms. In this reation best result is obtained when Both moleule are the same or ne should have no α-hydrogen atom and other should have at least two α-hydrogens. (b) These reations are pratial when base is Na and reation temperature is high ( 100 ). () The reation is two step reation. First step is aldol formation and seond step is dehydration of aldol. Na / Dehydration = a, β unsaturated aldehyde Due to hyper onjugation in rotonaldehyde further ondensed give onjugated alkene arbonyl ompound. = = Na = = = = = ( = ) ondensed ompound hapter 1 08

28 Aldehydes and Ketones Part The net result an be written as follows] Break arbon-arbon double bond between α and β arbons and attah two hydrogens on α-arbon Note : If produt is given then reatants an be known as follows : Mehanism : Step I : Step II : Step III : Suppose struture of produt is and an oxygen on β-arbon, i.e. β α = β α. / = = = / = rotonaldehyde / / = innamaldehyde In aldol ondensation, dehydration ours readily beause the double bond that forms is onjugated, both with the arbonyl group and with the benzene ring. The onjugation system is thereby extended. rossed aldol ondensation : Aldol ondensation between two different aldehydes or two different ketones or one aldehyde and another ketone provided al teast one of the omponents have α-hydrogen atom gives different possible produt = Benzalaetophenone hapter 1 09

29 Aldehydes and Ketones Part (a) dil Na Ethanal Propanal owever rossed aldol ondensation is important when only it the omponents has α-hydrogen atom. Intra moleular aldol ondensation : ne moleule Intramoleular ondensed give aldol ompounds Example : ( = ) (-hydroxy propanal) Na = (Arolein) (ii) laisen Shmidt reation : rossed aldol ondensation between aromati aldehyde and aliphati ketone or mixed ketone is known as laisen Shmidt reation. laisen Shmidt reations are useful when bases suh as sodium hydroxide are used beause under there onditions ketones do not undergo self ondensation. Some examples of this reation are : Geranial 100 = Phenylbuten--one / Test of aldehydes and Ketones (Distintion). = 1, Diphenyl propene-1-one Test Aldehydes Ketones 1. With Shiff's reagent Give pink olour. No olour.. With Fehling's solution Give red preipitate. No preipitate is formed.. With Tollen's reagent Blak preipitate of silver mirror is formed.. With saturated sodium bisulphite solution in water rystalline ompound (olourless) is formed.. With : -dinitrophenyl hydrazine range-yellow or red well defined rystals with melting points harateristi of individual aldehydes.. With sodium hydroxide Give brown resinous mass (formaldehyde does not give this test). 7. With sodium nitroprusside and few drops of sodium hydroxide A deep red olour (formaldehyde does not respond to this test). hapter 1 10 Pesudoionone = No blak preipitate or silver mirror is formed. rystalline ompound (olourless) is formed. range-yellow or red well defined rystals with melting points harateristi of individual ketones. No reation. Red olour whih hanges to orange.

30 Aldehydes and Ketones Part Some ommerially important aliphati arbonyl ompounds. Formaldehyde : Formaldehyde is the first member of the aldehyde series. It is present in green leaves of plants where its presene is supposed to be due to the reation of with water in presene of sunlight and hlorophyll. Traes of formaldehyde are formed when inomplete ombustion of wood, sugar, oal, et., ours. (1) Preparation (i) By oxidation of methyl alohol K r 7 [ ] S Platinised asbestos 0000 u or Ag (ii) By dehydrogenation of methyl alohol (iii) By heating alium formate : (iv) By ozonolysis of ethylene : (v) Manufature : ) alium formate eat 0000 a ( a Formaldehyde = Mo-oxide Methane atalyst Formaldehyde It is also prepared by passing water gas at low pressure through an eletri disharge of low intensity. Ele. disharge () Physial properties (i) It is a olourless, pungent smelling gas. (ii) It is extremely soluble in water. Its solubility in water may be due to hydrogen bonding between water moleules and its hydrate. (iii) It an easily be ondensed into liquid. The liquid formaldehyde boils at 1. (iv) It auses irritation to skin, eyes, nose and throat. (v) Its solution ats as antisepti and disinfetant. () hemial properties : Formaldehyde is struturally different from other aldehydes as it ontains no alkyl group in the moleule. Though it shows general properties of aldehydes, it differs in N ertain respets. The abnormal properties of formaldehyde are given below (i) Reation with ammonia : Like other aldehydes, formaldehyde does not form additon produt but a rystalline ompound, hexamethylene tetramine, with ammonia. N ( ) N Formaldehyde Urotropine (examethylene tetramine) hapter 1 11 zonide Pd N N Urotropine N

31 Aldehydes and Ketones Part examethylene tetramine has a yli struture. It is used as mediine in ase of urinary troubles under the name of Urotropine or hexamine. (ii) Reation with sodium hydroxide (annizzaro's reation) : It does not form resin with sodium hydroxide like aetaldehyde but when treated with a onentrated solution of sodium hydroxide, two moleules of formaldehyde undergo mutual oxidation and redution forming formi aid salt and methyl alohol (Disproportionation). Na Na Formaldehyde Sod. Formate Methyl alohol This transformation is known as annizzaro's reation. Tishenko's reation : This is a modified form of annizzaro's reation. All aldehydes undergo annizzaro's reation in presene of aluminium ethoxide. The aid and alohol formed reat together to give the ester. ( ) Al [ ] [ ] Al Butoxide Ethyl aetate (iii) Aldol ondensation : Formaldehyde in presene of a weak base undergo repeated aldol ondensation to give formose (α- arose). Formaldehyde a( ) 1 Formose (hexose) (iv) ondensation with phenol : Formaldehyde ondenses with phenol to give a syntheti plasti, bakelite. The ondensation ours in presene of dilute sodium hydroxide or ammonia at Bakelite is used for preparing eletrial insulators, eletri swithes, toys, et. Phenol Formaldehyde Base dil. K Bakelite Bakelite is eletrial and thermal resistant so it is used in formation of eletrial applianes. This reation is alled Lederer- Manasse reation. (v) ondensation with urea : Formaldehyde also ondenses with urea in aidi solution to form a plasti like produt. hapter 1 1

32 Aldehydes and Ketones Part m NN Urea n Formaldehyde N N (vi) Reation with alohol : Formaldehyde reats with methyl alohol in presene of dry hydrogen hloride or fused alium hloride forming methylal whih is used as soporifi. = Formaldehyde Methyl alohol Methylal (Dimethoxy methane) Formaldehyde- urea plasti (vii) Polymerisation : Formaldehyde readily undergoes polymerisation. N N N N (a) Paraformaldehyde : When an aqueous solution of formaldehyde is evaporated to dryness, a white rystalline solid with fishy odour is obtained. It is a long hain polymer. n Formaldehyde ( ) n Para-formaldehyde n = to 0 n rapid heating it gives bak gaseous formaldehyde. When a formaldehyde solution is treated with on. S are formed. n ( n ; n > 100 ). Polyoxy methylene This on heating gives bak formaldehyde., a white solid, polyoxy methylenes ( ) n. (b) Metaformaldehyde : n allowing formaldehyde gas to stand at room temperature, it slowly polymerises to metaform, (). It is a white solid (m.pt. 1 ). This on heating gives bak gaseous formaldehyde. Formaldehyde ) Meta- formaldehyde or trioxane ( or Trioxy methylene (trioxan) (viii) Reation with grignard reagent : Formaldehyde forms primary alohols with Grignard reagent. R = RMgI MgI R Mg Ether Primary alohol Formaldehyde does not reat with hlorine and phosphorus pentahloride. It does not give iodoform test. () Uses on. S heat (i) The 0% solution of formaldehyde (formalin) is used as disinfetant, germiide and antisepti. It is used for the preservation of biologial speimens. (ii) It is used in the preparation of hexamethylene tetramine (urotropine) whih is used as an antisepti and germiide. hapter 1 1 I

33 Aldehydes and Ketones Part (iii) It is used in silvering of mirror. (iv) It is employed in manufature of syntheti dyes suh as para-rosaniline, indigo, et. (v) It is used in the manufature of formamint (by mixing formaldehyde with latose) a throat lozenges. (vi) It is used for making syntheti plastis like bakelite, urea-formaldehyde resin, et. (vii) Rongalite a produt obtained by reduing formaldehyde sodium bisulphite derivative with zin dust and ammonia and is used as a reduing agent in vat dyeing. (ix) If aqeous solution of formaldehyde is kept with lime water in dark room for days then it onverts into (viii) As a methylating agent for primary and seondary amines, e.g., N N Ethylamine Ethyl methylamine a sweet solution alled formose or α-arose. It is an example of linear polymer. a( ) / Ba( ) Dark - days 1 Formose / α-arose Aetaldehyde Aetaldehyde is the seond member of the aldehyde series. It ours in ertain fruits. It was first prepared by Sheele in 177 by oxidation of ethyl alohol. below (1) Preparation : It may be prepared by any of the general methods. The summary of the methods is given (i) By oxidation of ethyl alohol with aidified potassium dihromate or with air in presene of a atalyst like silver at 00. (ii) By dehydrogenation of ethyl alohol. The vapours of ethyl alohol are passed over opper at 00. (iii) By heating the mixture of alium aetate and alium formate. (iv) By heating ethylidene hloride with austi soda or austi potash solution. (v) By the redution of aetyl hloride with hydrogen in presene of a atalyst palladium suspended in barium sulphate (Rosenmund's reation). (vi) By the redution of N with stannous hloride and l in ether and hydrolysis (Stephen's method). (vii) By hydration of aetylene with dil. S and gs at 0. (viii) By ozonolysis of butene- and subsequent breaking of ozonide. (ix) Laboratory preparation : Aetaldehyde is prepared in the laboratory by oxidation of ethyl alohol with aidified potassium dihromate or aidified sodium dihromate. K r7 S KS r( S ) [ ] [ ] K r7 S KS r( S ) 7 Potassium Ethyl alohol Sulphuri aid Potassium hromi Aetaldehyde Water dihromate sulphate sulphate To reover aetaldehyde, the distillate is treated with dry ammonia when rystallised produt, aetaldehyde ammonia, is formed. It is filtered and washed with dry ether. The dried rystals are then distilled with dilute sulphuri aid when pure aetaldehyde is olleted. hapter 1 1

34 Aldehydes and Ketones Part S N N ( N ) Aetaldehyde ammonia Aetaldehyde S (x) Manufature : Aetaldehyde an be manufatured by one of the following methods: (a) By air oxidation of ethyl alohol : Ethyl alohol vapours and limited amount of air are passed over heated silver atalyst at 00. (b) By dehydrogenation of alohol : Vapours of ethyl alohol are passed over heated opper at 00. u Ag () By hydration of aetylene : Aetylene is passed through water ontaining 0% sulphuri aid and 1% meruri sulphate at 0 when aetaldehyde is formed. gs,(1%),0 S (0%) (d) From ethylene (Waker proess) : Ethylene is passed through an aidified aqueous solution of palladium hloride and upri hloride, when aetaldehyde is formed. (So = Pdl ul Pd ul Pdl ul Pd 1 ul l ul = Ethylene 1 Aetaldehyde Pdl, ul ) = () Physial properties (i) Aetaldehyde is a olourless volatile liquid. It boils at 1. (ii) It has a harateristi pungent smell. l (iii) It is soluble in water, hloroform, ethyl alohol and ether. Its aqueous solution has a pleasant odour. In water, it is hydrated to a onsiderable extent to form ethylidene glyol. () () hemial properties : It gives all harateristi reations of aldehydes. Besides general reations, aetaldehyde shows the following reations also. (i) aloform reation : It responds to iodoform reation due to the presene of (ii) Tishenko's reation : It forms ethyl aetate in presene of aluminium ethoxide. ( ) Al Ethyl aetate group. hapter 1 1

35 Aldehydes and Ketones Part (iii) hlorination : ydrogen atoms of the methyl group are substituted by hlorine atoms when aetaldehyde is treated with hlorine. l l l hloral (iv) Polymerisation : Aetaldehyde undergoes polymerisation forming different produts under different onditions. (a) Paraldehyde : It is formed, when anhydrous aetaldehyde is treated with on. sulphuri aid. Aetaldehyde ( ) Paraldehyde, (trimer) It is a pleasant smelling liquid (b.pt. 1 ). It has yli struture and when heated with dilute sulphuri aid it hanges again into aetaldehyde. It is used as a hypnoti and soporifi (sleep produing). Reation with N : N N N = N = Aetaldimine N N N N Trimethyl hexa hydro triazine [Trihydrate]. (b) Metaldehyde : Aetaldehyde on treatment with hydrogen hloride or sulphur dioxide is onverted into metaldehyde ( ). It is a white solid (m. pt. ). n heating it sublimes but hanges again into aetaldehyde when distilled with dilute sulphuri aid. It is used as a solid fuel. Aetaldehyde It is used for killing slugs and snails. () Uses : Aetaldehyde is used : Metaldehyde (textramer) hapter 1 1

36 Aldehydes and Ketones Part (i) In the preparation of aeti aid, aeti anhydride, ethyl aetate, hloral, 1,-butadiene (used in rubbers), dyes and drugs. (ii) As an antisepti inhalent in nose troubles. (iii) In the preparation of paraldehyde (hypnoti and sporofi) and metaldehyde (solid fuel). S.No. Reation Formaldehyde Aetaldehyde (iv) In the preparation of aetaldehyde ammonia (a rubber aelerator). 1. Similarty Addition of hydrogen (a) in presene of atalyst, Ni, Pd or Pt (b) LiAl (ether) () Amalgamated zin on. l (lemmensen redution). Addition of NaS solution omparative study of formaldehyde and aetaldehyde Forms methyl alohol Forms methane Forms bisulphite addition produt NaS ( ) S Na. Addition of N Forms formaldehyde yanohydrin. Addition of Grignard reagent followed by hydrolysis N ( ) N Forms ethyl alohol MgI Mg( ) I MgI Forms ethyl alohol Forms ethyl alohol Forms ethane Forms bisulphite addition produt NaS ( ) S Na Forms aetaldehyde yanohydrin N ( ) N Forms isopropyl alohol MgI MgI Mg( ) I. With hydroxylamine N Forms formaldoxime = N Forms aetaldoxime = N = N. With hydrazine ( N N ) Forms formaldehyde hydrazone N N = NN = N Forms aetaldehyde hydrazone = NN = NN 7. With phenyl hydrazine ( NN ) Forms formaldehyde phenyl hydrazone = NN = NN Forms aetaldehyde phenyl hydrazone = NN = NN hapter 1 17

37 Aldehydes and Ketones Part 8. With semiarbazide Forms formaldehyde semiarbazone ( NNN ) = NNN 9. With alohol ( ) in presene of aid = NNN Forms ethylal = l Forms aetaldehyde semiarbazone = NNN = NNN Forms aetaldehyde diethyl aetal l 10. With thioalohols ( S) in presene of aid Forms thio ethylal = S S S 11. xidation with aidified K r7 Forms formi aid 1. With Shiff's reagent Restores pink olour of Shiff's reagent 1. With Tollen's reagent Gives blak preipitate of Ag or silver mirror 1. With Fehling's solution or Benedit's solution Ag Ag Gives red preipitate of uprous oxide u u 1. Polymerisation Undergoes polymerisation 1. n ( ) n Paraformaldehyde Room temp. () Metaformaldehyde Evaporation Forms aetaldehyde diethyl thioaetal = S S S Forms aeti aid Restores pink olour of Shiff's reagent Gives blak preipitate of Ag or silver mirror Ag Ag Gives red preipitate of uprous oxide u u Undergoes polymerisation ( Paraldehyd ) e ( ) Metaldehyde Differene With Pl No reation Forms ethylidene hloride heat S on. dil. S. distill Pl l l Pl 17. With hlorine No reation Forms hloral hapter 1 18 l l l

38 Aldehydes and Ketones Part 18. With Se No reation Forms glyoxal Se. Se 19. Iodoform reation (I Na) No reation Forms iodoform 0. With dil. alkali (Aldol ondensation) 1. With on. Na (annizzaro's reation) No reation Forms sodium formate and methyl alohol Na Na. With ammonia Forms hexamethylene tetramine (urotropine) N ( ) N I Na l Na NaI Forms aldol ( ) Forms a brown resinous mass Forms addition produt, aetaldehyde ammonia N. With phenol Forms bakelite plasti No reation. With urea Forms urea-formaldehyde plasti No reation. ondensation in presene of a () Form formose (a mixuture of sugars) No reation Inter onversion of formaldehyde and aetaldehyde (1) Asent of series : onversion of formaldehyde into aetaldehyde (i) Formaldehyde / Ni Pl Al. KN Na / Alohol N l N N Methyl alohol Methyl hloride Methyl yanide Ethyl alohol Ethyl amine S (dil.) 7 NaN l K r Aetaldehyde (ii) (iii) Formaldehyde Formaldehyde MgI u MgI Ether K r Formi aid a( ) Ethyl alohol alium formate 00 ( ) a heat Aetaldehyde 7 ) ( a S Aetaldehyde () Desent of series : onversion of aetaldehyde into formaldehyde (i) K r 7 N Aetaldehyde S Aeti aid N Amm. aetate eat N N Methyl amine Aetamide NaN l Br / K u 00 Formaldehyde hapter 1 19