Chapter 22. Organic and Biological Molecules

Transcription

1 hapter 22 Organic and Biological Molecules

2 hapter 22 Preview Organic and Biological Molecules Alkanes: Saturated ydrocarbons Isomerism, Nomenclature, Reactions of alkanes, yclic alkanes Alkenes, Alkynes, and Aromatic ydrocarbons Reaction of alkenes and alkynes ydrocarbon Derivatives Alcohols, Aldehydes and ketones, arboxylic acids and esters, and amines Polymers and Natural Polymers Properties of polymers, Types of polymers, plymers based on ethylene, Protein, arbohydrates, and Nucleic Acids

3 Introduction What is Organic hemistry? It is defined as the study of hydrocarbons (compounds of hydrogen and carbon) and their derivatives Late 18 th century: ompounds from living organisms - Organic ompounds from lifeless matter Inorganic Organic compounds thought to have vital force Wöhler Ammonium cyanate (from mineral sources) Inorganic (eat) Urea (from urine) Organic

4 Organic chemicals are universal Biological matter Plants Animals Microbes Geological matter Fossil Fuels Other Organic hemicals Manufactured products Atmospheric and cosmic matter

5 22.1 Alkanes: Saturated ydrocarbon Alkanes n 2n+2 consist of only carbon and hydrogen bonded by single covalent bonds single methane ethane propane butane pentane n-alkanes are all gases Methane main component of natural gas Propane and butane often stored as compressed gases Skeletal structure of only carbon atoms propane butane pentane

6 n 1 Molecular Formula 4 Structural formula methane Name ondensed structural formula ethane propane butane pentane hexane

7 Further members of the series eptane Octane Nonane Decane Undecane Dodecane Etc., etc.

8 Isomerism Isomers are molecules that have the same molecular formula but different structures

9 Extent of structural isomerism in alkanes Alkane Methane 1 Ethane 1 Propane 1 Butane 2 Pentane 3 exane 5 Decane 75 No. of structural isomers Pentadecane 4347 Eicosane 366,319 Triacontane 44 x 10 9 ( ) All known

10 Pentane structural isomers All of these based on tetrahedral (sp 3 hybridised) arbon No other arrangements of 5 12 possible Note = = etc.

11 ow many structural isomers does pentane, 5 12, have? n-pentane ,2-dimethylpropane 2-methylbutane

12 Nomenclature 1. The parent name of the hydrocarbon is that given to the longest continuous chain of carbon atoms in the molecule methylheptane ommon Alkyl Groups 2. An alkane minus one hydrogen atom is called an Alkyl group 4 methane 3 methyl

13 Nomenclature 3. When one or more hydrogen atoms are replaced by other groups, the name of the compound must indicate the locations of carbon atoms where replacements are made. Number in the direction that gives the smaller numbers for the locations of the branches methylpentane methylpentane

14 Nomenclature 4. Use prefixes di-, tri-, tetra-, when there is more than one alkyl branch of the same kind ,3-dimethylhexane ,3-dimethylhexane

15 Nomenclature 5. Use previous rules for other types of substituents. Br NO 2 Names of ommon Groups bromo-3-nitrobutane Br NO bromo-3-nitrobutane

16 Nomenclature Rules for Naming Alkanes: 1. Names after butane are obtained by adding the suffix ane to the Greek root for the nyumber of carbon atoms (pent- for five, hex- for six ) 2. For a branched carbon hydrocarbons, the name is given for the longest continuous chain 3. When they are substituents, the ane is replaced with -yl 4. The positions of substituent groups are specified by numbering the longest chain starting from the closest end. 5. The location and names of each substituent are followed by the root alkane name and they have to be listed in alphabetical order, and the prifix di-, tri- for multiple ,2,4-Trimethylpentane ,4-dimethyl-4-ethylhexane

17 Questions What is the IUPA name of the following compound? What is the structure of 2-propyl-4-methylhexane?

18 ombustion reaction 4 (g) + 2O 2 (g) Alkane Reactions Alkanes are fairly uncreative, but at sufficient high temperature react vigorously and exothermically with oxygen Substitution reaction 4 (g) + l 2 (g) light l 2 + energy l + l l + O 2 (g) O (l) 0 = kj 3 l (g) + l (g) + l Substitution reaction Formation of unsaturated hydrocarbons = Using r 2 O 3 at high temperature + l l l + l Freons F x l 4-x

19 yclic Alkanes Alkanes whose carbon atoms are joined in rings are called yclic Alkanes. They have the general formula n 2n where n = 3,4,

20 22.2 Alkene and Alkyne Alkene have the general formula n 2n where n = 2,3, contain at least one carbon-carbon double bond and the systematic names are ethene, propene, butene 2-butene have restricted rotation around the double bond to produce cis-trans isomerisms l l cis-dichloroethylene l l trans-dichloroethylene

21 Alkyne Alkyne have the general formula n 2n-2 where n = 2,3,4, contain at least one carbon-carbon triple bond and the systematic names are ethyne, propyne, butyne 2-butyne Reactions of alkenes and alkynes ydrogenation (g) + 2 (g) 2 2 (g) alogenation Reactions 2 2 (g) + Br 2 (g) 2 Br 2 Br (g) Polymerization Small molecules are joined together to form large molecules

22 22.3 Aromatic ydrocarbons A special class of cyclic unsaturated hydrocarbons Benzene is the simplest The delocalized p-electrons make it different than the other unsaturated hydrocarbons Benzene does not present the addition reactions

23 Aromatic ompound Nomenclature ethylbenzene aminobenzene 2 3 l N 2 NO 2 chlorobenzene nitrobenzene Br Br Br ,2-dibromobenzene Br 1,3-dibromobenzene

24 Aromatic ompound Reactions Substitution reaction Br + Br 2 FeBr 3 catalyst + Br l All 3 catalyst + l

25 Polycyclic Aromatic ydrocarbons

26 22.4 ydrocarbon Derivatives ydrocarbons that have additional atoms or groups different than arbon and hydrogen (functional group) The common functional groups are. They exhibit characteristic chemistry

27 Alcohols contain the hydroxyl functional group and have the general formula R-O. The systematic name is obtained from parent alkane by removing the final letter e and adding ol. Biological production of ethanol 6 12 O 6 (aq) enzyme O (aq) + 2O 2 (g) ommercial production of ethanol 2 SO (g) + 2 O (g) 3 2 O (g) Metabolic oxidation of ethanol alcohol dehydrogenase 3 2 O 3 O + 2

28 Aldehyde and Ketones They contain carbonyl functional group. Aldehyde have the general formula Ketone have the general formula O O O R O R R The systematic name of aldehyde is obtained from parent alkane by removing the final letter e and adding al, and for ketone also by removing the final letter e and adding one O

29 arboxylic acids and Esters they contain the carboxyl functional group. The systematic name is obtained from parent alkane by removing the final letter e and adding oic. The esters are formed, if carboxylic acid reacts with alcohol: O 3 OO + O O O ethyl acetate The systematic name is obtained from parent alkane by removing the final letter oic and adding oate of the acid, e.g., ethyl ethanoate.

30 Amines They are organic bases with the general formula RN 2 The common names are often used for simple amines, and the systematic name is obtained by using the name amino for each N2 group, e.g., 2-aminobutane They are used for making dyes and their main reaction is acid-base: 3 N O RN 3+ + O N 2 + l 3 2 N 3+ l -

31 22.5 Polymers A polymer is a high molar mass molecular compound made up of many repeating chemical units. Naturally occurring polymers Proteins Nucleic acids ellulose Rubber Synthetic polymers Nylon Dacron Lucite

32 The simple repeating unit of a polymer is the monomer. omopolymer is a polymer made up of only one type of monomer ( F 2 F 2 ) n ( 2 2 ) n ( 2 ) n Teflon Polyethylene l PV

33 Stereoisomers of Polymers R groups on same side of chain Isotactic R groups alternate from side to side Syndiotactic R groups disposed at random Atactic

34 22.2

35 Proteins Amino acids are the basic structural units of proteins. An amino acid is a compound that contains at least one amino group (-N 2 ) and at least one carboxyl group (-OO) O O + 3 N O N O - R 1 R 2 Peptide bond O O + 3 N N O O R 1 R

36 22.3

37 Protein Structure arbon Nitrogen Oxygen R group The structure is held in position by intramolecular hydrogen bonds ( ) ydrogen 22.3

38 Protein Structure 22.3

39 Protein Structure Intermolecular Forces in a Protein Molecule ionic forces hydrogen bonds dispersion forces dispersion forces dispersion forces dipole-dipole forces ionic forces 22.3

40 ydrogen Bonds in Parallel and Antiparallel β-pleated Sheets 22.3

41 Protein Structure The structural changes that occur when oxygen binds to the heme group in hemoglobin. 22.3

42 Nucleic Acids Nucleic acids are high molar mass polymers that play an essential role in protein synthesis. 1. Deoxyribonucleic acid (DNA) 2. Ribonucleic acid (RNA) DNA molecule has 2 helical strands. Each strand is made up of nucleotides. 22.4

43 The omponents of the Nucleic Acids DNA and RNA 22.4

44 Base-Pair Formation by Adenine and Thymine and by ytosine and Guanine 22.4

45 hemistry In Action: DNA Fingerprinting 22.4