Chapter 22. Organic and Biological Molecules

Transcription

1 Chapter 22 Organic and Biological Molecules 1

2 Organic Chemistry and Biochemistry The study of carbon-containing compounds and their properties. The vast majority of organic compounds contain chains or rings of carbon atoms. The study of the chemistry of living matter 2

3 Hydrocarbons compounds composed of carbon and hydrogen. Saturated compounds (alkanes) have the maximum number of hydrogen atoms attached to each carbon atom H H H C C H H H 3

4 Unsaturated compounds have fewer hydrogen atoms attached to the carbon chain than alkanes Unsaturated: They contain carbon-carbon multiple bonds (double or triple) H H C H H C C H H 4

5 22.1 Alkanes: Saturated hydrocarbons Saturated hydrocarbons, C n H 2n+2 Saturated because they can t take any more hydrogen atoms Normal straight chains (unbranched hydrocarbons) H 3 C (CH 2 ) n 2 CH 3 Waxes, oils, & fuel gases as n decreases. 5

6 Alkanes: Saturated Hydrocarbons The C-H Bonds in Methane 6

7 The Lewis structure of ethane. 7

8 Propane 8

9 Butane 9

10 The First 10 Normal Alkanes Name Formula M.P. B.P. # Structural Isomers Methane CH Ethane C 2 H C1 - C4 are Gases Propane C 3 H at Room Temperature Butane C 4 H Pentane C 5 H Hexane C 6 H Heptane C 7 H Octane C 8 H C5 - C16 are Liquids Nonane C 9 H at Room Temperature Decane C 10 H

11 IUPAC Rules for Naming Branched Alkanes Find and name the parent chain in the hydrocarbon - this forms the root of the hydrocarbon name Number the carbon atoms in the parent chain starting at the end closest to the branching Name alkane branches by dropping the ane from the names and adding yl. A one-carbon branch is called methyl, a two-carbon branch is ethyl, etc When there are more than one type of branch (ethyl and methyl, for example), they are named alphabetically Finally, use prefixes to indicate multiple branches 11

12 Rules for Naming Alkanes 1. For alkanes beyond butane, add -ane to the Greek root for the number of carbons. C-C-C-C-C-C : hexane 2. Alkyl substituents: drop the -ane and add -yl -C 2 H 5 is ethyl 12

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14 Rules for Naming Alkanes 3. Positions of substituent groups are specified by numbering the longest chain sequentially. C C-C-C-C-C-C 3-methylhexane Start numbering at the end closest to the branching 4. Location and name are followed by root alkane name. Substituents are given in alphabetical order and use di-, tri-, etc. 14

15 Normal vs Branched Alkanes CH 3 CH 2 CH2 CH 2 CH3 CH 3 CH 2 CH CH 3 CH 3 Normal alkanes consist of continuous chains of carbon atoms Alkanes that are NOT continuous chains of carbon atoms contain branches The longest continuous chain of carbons is called the parent chain 15

16 Structural Isomerism Structural isomers are molecules with the same chemical formulas but different molecular structures - different connectivity. They arise because of the many ways to create branched hydrocarbons. CH 3 CH 2 CH2 CH 2 CH3 n-pentane, C 5 H 12 CH 3 CH 2 CH CH 3 CH 3 2-methlbutane, C 5 H 12 16

17 Example : Show the structural formula of 2,2-dimethylpentane The parent chain is indicated by the ROOT of the name - pentane. This means there are 5 carbons in the parent chain. CH 3 C 4 CH CH 3 CH 2 CH2 CH 2 CH3 dimethyl tells us that there are TWO methyl branches on the parent chain. A methyl branch is made of a single carbon atom CH 3 CH 3 CH 3 2 CH 5 3 2,2- tell us that BOTH methyl branches are on the second carbon atom in the parent chain. 17

18 Example: Structural formula of 3-ethyl-2,4-dimethylheptane? The parent chain is indicated by the ROOT of the name - heptane. This means there are 7 carbons in the parent chain CH 3 CH 2 CH2 CH 2 CH2 5 H C6 2 7 CH 3 CH 3 CH CH 3 CH 3 CH CH CH 2 2,4-dimethyl tells us there are TWO methyl branches on the parent chain, at carbons #2 and #4. CH 3 CH 2 CH 2 CH3 3-ethyl- tell us there is an ethyl branch (2-carbon branch) on 18 carbon #3 of the parent chain.

19 Example: 2,3,3-trimethyl-4-propyloctane The parent chain is indicated by the ROOT of the name - octane. This means there are 8 carbons in the parent chain ,3,3-trimethyl CH 3 tells us there are CH THREE 3 methyl C branches CH 2 - one on carbon CH#2 and CH two on carbon CH2 #3. CH 3 CH 3 CH2 CH 2 CH3 4-propyl- tell us there is a propyl branch (3-carbon branch) CH 2 on carbon #4 of the parent chain. CH 3 19

20 Example : Name the molecules shown parent chain has 5 carbons - pentane two methyl branches - start counting from the right - #2 and #3 2,3-dimethylpentane CH 3 CH 2 CH CH 3 CH 3 CH CH 3 parent chain has 8 carbons - octane two methyl branches - start counting from the left - #3 and #4 one ethyl branch - #5 name branches alphabetically 5-ethyl- 3,4-dimethyl octane 20

21 Reactions of alkanes Combustion reactions 2C 4 H O 2 8CO H 2 O(g) Substitution Reactions CH 4 + Cl 2 CH 3 Cl + Cl 2 CH 2 Cl 2 + Cl 2 CH 3 Cl + HCl CH 2 Cl 2 + HCl CH Cl 3 + HCl CHCl 3 + Cl 2 C Cl 4 21

22 Dehydrogenation Reactions CH 3 CH 3 CH 2 CH 2 Ethylene 22

23 Cyclic alkanes C n H 2n A cycloalkane is made of a hydrocarbon chain that has been joined to make a ring bond angle H 2 C CH 2 CH 3 CH 3 H 2 C CH 2 n-propane C 3 H 8 cyclopropane C 3 H 6 60 bond angle unstable!! Note that two hydrogen atoms were lost in forming the ring 23

24 Ring Structures 24

25 Cyclohexane - Boat & Chair Conformations Cyclohexane is NOT a planar molecule. To achieve its bond angles and reduce angle strain, it adopts several different conformations. The BOAT and CHAIR (99%) are two conformations Boat chair 25

26 22.2 Alkenes and Alkynes Alkenes: hydrocarbons that contain a carbon-carbon double bond. [C n H 2n ] C=C CC=C Ethene propene Alkynes: hydrocarbons containing a carbon-carbon triple bond. [C n H 2n-2 ] C ΞC CCC Ξ CC Ethyne 2-pentyne 26

27 Alkenes & Alkynes Alkenes are hydrocarbons that contain at least one carbon-carbon double bond Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond The suffix for the parent alkane chains are changed from ane to ene and yne e.g. ethene, ethyne Where it is ambiguous, the BONDS are numbered like branches so that the location of the multiple bond may be indicated 27

28 Alkenes, C n H 2n Cycle formation isn t the only possible result of dehydrogenation. Adjacent C s can double bond, C=C, making an (unsaturated) alkene. Sp 2 28

29 Nomenclature for Alkenes 1. Parent hydrocarbon name ends in -ene C 2 H 4; CH 2 =CH 2 is ethene 2. With more than 3 carbons, double bond is indicated by the lowest numbered carbon atom in the bond. C=C-C-C is 1-butene 29

30 Nomenclature alkenes and alkynes 30

31 Cis and Trans Isomers Double bond is fixed (rotation around the double bond is restricted) Cis/trans Isomers are possible CH 3 CH 3 CH 3 CH = CH CH = CH cis trans CH 3 31

32 Reactions of alkenes and alkynes 1. Addition Reactions in which (weaker) bonds are broken and new (stronger) bonds are formed to atoms being added. 32

33 Hydrogenation reaction Adds a hydrogen atom to each carbon atom of a double bond H H catalyst H C=C H + H 2 Ethene H H H C C H H H Ethane CH 3 -CH 3 33

34 Halogenation reaction Adds a halogen atom to each carbon atom of a double bond H H H C=C H + Cl 2 catalyst H H H C C H Cl Cl Ethene Dichloro ethane 34

35 Halogenation Reactions CH 2 CHCH 2 CH 2 CH 2 + Br 2 CH 2 Br CHBrCH 2 CH 2 CH 2 1,2-dibromopentane 35

36 Alkynes, C n H 2n 2 sp triple bonding makes a rigid 180 segment in a hydrocarbon. Carbon-carbon triple bonds Names end in -yne HC CH HC C-CH 3 ethyne(acetylene) propyne 36

37 The Bonding in Acetylene 37

38 Naming Alkenes and Alkynes When the carbon chain has 4 or more C atoms, number the chain to give the lowest number to the double or triple bond CH 2 =CHCH 2 CH 3 CH 3 CH=CHCH 3 1-butene 2-butene CH 3 CH CHCH 3 2-butyne 38

39 Question Write the IUPAC name for each of the following unsaturated compounds: A. CH 3 CH 2 C CCH 3 CH 3 2-pentyne CH 3 B. CH 3 C=CHCH 3 C. 2-methyl-2-butene 3-methylcyclopentene 39

40 Question Name the following compound CH 3 CH 2 C CCHCH 2 CH 3 CH 2 CH CH 3 CH 2 C CCHCH 2 CH 3 CH 2 CH 3 5-ethyl-3-heptyne 40

41 Additions reactions:hydrogenation and Halogenation Hydrogens and halogens also add to the triple bond of an alkyne. Br Br CH 3 C CCH 2 CH 3 + Br 2 CH 3 C CCH 2 CH 3 Br Br 41

42 22.3 Aromatic hydrocarbons Unsaturated Cyclic hydrocarbons Alternating single/double bond cycles occur in many organic molecules This class is called aromatic (by virtue of their aroma). Delocalized bonds possess a great stability thus benzene does not react like unsaturated hydrocarbons 42

43 Benzene C 6 H 6 sp 2 The structure is often preserved in benzene chemical reactions Aromatic rings do not add, they substitute instead sp 2 sp 2 43

44 Shorthand notation for benzene rings The bonding in the benzene ring is a combination of different Lewis structures 44

45 Aromatic Hydrocarbons Substitution reaction Nitroobenzene benzene FeCl 3 + Cl 2 H N O 3 HNO 3 CH 3 Cl Chlorobenzene Cl + HCl +H 2 O +HCl -NO 2 -CH3 Toluene 45

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47 Nomenclature of benzene derivatives 47

48 More Complex Aromatic Systems 48

49 22.4 Hydrocarbon Derivatives (Functional Groups) Molecules that are fundamentally hydrocarbons but have additional atoms or group of atoms called functional groups Part of an organic molecule where chemical reactions take place Replace an H in the corresponding alkane Provide a way to classify organic compounds 49

50 The Common Functional Groups Class Halohydrocarbons Alcohols Ethers General Formula R X R OH R O R O Aldehydes R C H 50

51 Class Ketones General Formula O R C R' Carboxylic Acids Esters O R C O R C OR' OH Amines R NH 2 51

52 Some Types of Functional Groups Haloalkane -F, -Cl, -Br CH 3 Cl Alcohol -OH CH 3 OH Ether -O- CH 3 -O-CH 3 Aldehyde O C H O CH 3 CH Ketone O O C CH 3 CCH 3 52

53 More Functional Groups Carboxylic acid -COOH CH 3 COOH Ester -COO- CH 3 COOCH 3 Amine -NH 2 CH 3 NH 2 Amide -CONH 2 CH 3 CONH 2 53

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55 Haloahydrocarbons An alkane in which one or more H atoms is replaced with a halogen (F, Cl, Br, or I) CH 3 Br Br bromomethane (methyl bromide) CH 3 CH 2 CHCH 3 2-bromobutane Cl chlorocyclobutane 55

56 Name the following: Br bromocyclopentane Cl Cl 1,3-dichlorocyclohexane 56

57 Substituents List other attached atoms or groups in alphabetical order Br = bromo, Cl = chloro Cl Br CH 3 CHCH 2 CHCH 2 CH 2 CH 3 4-bromo-2-chloroheptane 57

58 Nomenclature The name of this compound is: Cl CH 3 CH 3 CH 2 CHCH 2 CHCH 3 4-chloro-2-methylhexane 58

59 Alcohols: R OH The OH makes alcohol polar enough to hydrogen bonding Thus, they are water soluble Ethanol is produced by the fermentation of glucose C 6 H 12 O 6 Glucose yeast 2CH 3 CH 2 OH Ethanol + 2 CO 2 Methanol is produced industrially by hydrogenation of carbon monoxide CO + 2H 2 O CH 3 OH Methanol 59

60 Uses of alcohols Methanol is used to synthesize adhesives, fibers, plastics and recently as motor fuel It is toxic to human and can lead to blindness and death Ethanol can be added to gasoline to form gasohol and used in industry as solvent Commercial production of ethanol: CH 2 =CH 2 + H 2 O CH 3 CH 2 OH 60

61 Classes of alcohols Alcohols can be classified according to the number of hydrocarbon fragments bonded to the carbon where the OH group is attached R CH 2 OH Primary alchol R R' R' CHOH Secondary alcohol R C R" OH Tertiary alcohol 61

62 Naming Alcohols In IUPAC name, the -e in alkane name is replaced with -ol. CH 4 methane CH 3 OH methanol CH 3 CH 3 ethane CH 3 CH 2 OH ethanol (methyl alcohol) (ethyl alcohol) 62

63 OH Phenol (Aromatic alcohol) 63

64 Some Typical Alcohols OH Rubbing alcohol CH 3 CHCH 3 2-propanol (isopropyl alcohol) Antifreeze HO-CH 2 -CH 2 -OH 1,2-ethanediol (ethylene glycol) 64

65 Naming Alcohols IUPAC names for longer chains number the chain from the end nearest the -OH group. CH 3 CH 2 CH 2 OH 1-propanol OH CH 3 CHCH 3 CH 3 OH 2-propanol 5 2 CH 3 CHCH 2 CH 2 CHCH 3 5-methyl-2-hexanol 65

66 Example Name the following alcohols: OH CH 3 CHCHCH 2 CH 3 CH 3 3-methyl-2-pentanol 66

67 Aldehydes and Ketones In an aldehyde, an H atom is attached to a carbonyl group O carbonyl group CH 3 -C-H In a ketone, two carbon groups are attached to a carbonyl group O CH 3 -C-CH 3 carbonyl group 67

68 Naming Aldehydes IUPAC name: Replace the -e in the alkane name by -al Common Add aldehyde to the prefixes form (1C), acet (2C), propion(3), and butry(4c) O O O ethane propane H-C-H CH 3 -C-H CH 3 CH 2 C-H methanal ethanal propanal (formaldehyde) (acetaldehyde) (propionaldehyde) methane 68

69 Aldehydes as Flavorings O CH O CH O CH=CH CH HO OCH 3 Benzaldehyde Vanillin Cinnamaldehyde (almonds) (vanilla beans) (cinnamon) 69

70 Naming Ketones IUPAC name: the -e in the alkane name is replaced with one and a number to indicate the position of carbonyl group when needed. In the common name, add the word ketone after naming the alkyl groups attached to the carbonyl group O O CH 3 -C-CH 3 CH 3 -C-CH 2 -CH 3 2-Propanone 2-Butanone (Dimethyl ketone) (Ethyl methyl ketone) Acetone propane butane O cyclohexane Cyclohexanone 70

71 Name the following compounds O A. CH 3 CH 2 CCH 3 B. 2-butanone (ethyl methyl ketone) CH 3 O C. CH 3 -C-CH 2 CH CH 3 3,3-dimethylbutanal O cyclohexanone 71

72 Draw the structural formulas for each of the following compounds CH 3 A. 3-Methylpentanal CH 3 CH 2 CHCH 2 CH Br O B. 2,3-Dibromopropanal Br-CH 2 CHCH O C. 3-Methyl-2-butanone CH 3 CHCCH 3 O CH 3 72

73 Preparation of aldehydes and Ketones They are produced by oxidation of alcohols: CH 3 CH 2 OH Primary alcohol Oxidation O CH 3 C H acetaldehyde ethanal CH 3 CHCH 3 OH Oxidation CH 3 CCH 3 O acetone propanone Secondary alcohol 73

74 Carboxylic Acids and Esters Carboxylic acids contain the carboxyl group as carbon 1. R O CH 3 C OH CH 3 COOH General formula carboxyl group R COOH 74

75 Nomenclature of Carboxylic Acids Formula IUPAC Common alkan -oic acid prefix ic acid HCOOH methanoic acid formic acid CH 3 COOH ethanoic acid acetic acid CH 3 CH 2 COOH propanoic acid propionic acid CH 3 CH 2 CH 2 COOH butanoic acid butyric acid 75

76 IUPAC nomenclature for Carboxylic acids Identify longest chain Number carboxyl carbon as 1 CH CH 3 CH CH 2 COOH 1 3-methylbutanoic acid 76

77 CH 3 CH 3 CHCOOH 2-methylpropanoic acid; 77

78 Reaction of carboxylic acid with alcohol Esterification O CH 3 C Carboxylic acid OH + H OCH 2 CH 3 Alcohol O CH 3 C OCH 2 CH 3 + H 2 O Ester 78

79 Esters In ester, the H in the carboxyl group is replaced with an alkyl group O CH 3 C O CH 3 CH 3 COO CH 3 ester group Esters give fruity odors 79

80 Naming Esters The parent alcohol is named first with a yl ending Change the oic ending of the parent acid to ate acid alcohol O methyl CH 3 C O CH 3 Ethanoate (acetate) methyl ethanoate (IUPAC) methyl acetate (common) 80

81 Amines Organic compounds of nitrogen N; derivatives of ammonia Classified as primary, secondary, tertiary CH 3 CH 3 CH 3 NH 2 CH 3 NH CH 3 N CH 3 Primary Secondary Tertiary one N-C two N-C three N-C bond bonds bonds 81

82 Naming Amines IUPAC aminoalkane CH 3 CH 2 NH 2 aminoethane (ethylamine) Common alkylamine NH 2 NH 2 CH 3 CHCH 3 2-aminopropane (isopropylamine) Aniline 82

83 22.5 Polymers Poly= many; mers=parts Polymers are large, usually chainlike molecules that are built from small molecules called monomers joined by covalent bonds Monomer Ethylene Vinyl chloride Tetrafluoroethylene Polymer Polyethylene Polyvinyl chloride Teflon 83

84 Some common synthetic polymers, their monomers and applications 84

85 Types of Polymerization Addition Polymerization: monomers add together to form the polymer, with no other products. ( Polyethylene and Teflon) Condensation Polymerization: A small molecule, such as water, is formed for each extension of the polymer chain. (Nylon) 85

86 H H H H C OH H C H C OH C Addition Polymerization C H C H H H H H H H C OH H C The polymerization process Is initiated by a free radical H H H C OH H C H A species with an unpaired electron such as hydroxyl free radical H H C C H H Free radical attacks and break The bond of ethylene molecule To form a new free radical Repetition of the process thousands of times creates a long chain polymer The process is terminated when two radicals react to form a bond; thus there will be no free radical is available for further repetitions. 86

87 H N H Condensation Polymerization Formation of Nylon (CH 2 ) 6 N H O H C H O Hexamethylendiamine H N H Diamine (CH 2 ) 6 H N Dimer (CH 2 ) 4 O C (CH 2 ) 4 C O O H C O O H Adipic acid Dicarboxylic acid + H 2O Small molecule such as H 2 O is formed from each extension of the polymer chain both ends are free to react 87

88 Nylon H H O ( N (CH 2 ) 6 N O C (CH 2 ) 4 C ) n 88