西北农林科技大学：《有机化学 Organic chemistry》课程PPT教学课件（2014）Chapter 04 Structure and Stereochemistry of Alkanes

有机化学oRcAn1©©ⅫEMISTRY 孟饼：王依儒87092829l 理学院爱化素理科接2层206 Organic Chemistry,6th Edition L.G.Wade,Jr. Chapter 4 Structure and Stereochemistry of Alkanes Key Notes Mechanisms;Conformation;Ring strain; Conformers;Cis-trans isomers;

Chapter 4 Structure and Stereochemistry of Alkanes Key Notes Mechanisms; Conformation; Ring strain; Conformers; Cis-trans isomers; Organic Chemistry, 6th Edition L. G. Wade, Jr. 有机化学ORGANIC CHEMISTRY 主讲：王俊儒 87092829(o) 理学院应化系理科楼2层C206

自秋转对 CONTENTS 教华税 Classification of Hydrocarbons ■Physical properties Reactions Mechanisms of Alkanes Structure Conformation of Alkanes Conformation of Cycloalkanes Homework: 4-7140:4-16;:4-18(a,b,d):P147)

CONTENTS ◼Classification of Hydrocarbons ◼Physical properties ◼Reactions & Mechanisms of Alkanes ◼Structure & Conformation of Alkanes ◼Conformation of Cycloalkanes Homework: 4-7(P140); 4-16; 4-18（a,b,d）;(P147))

Hydrocarbons Hydrocarbons are molecules that are made of carbon and hydrogen ONLY. TABLE 3-1 Hydrocarbon Classifications Compound Type Functional Group Example alkanes none(no double or triple bonds) CH3-CH2-CH3,propane alkenes C-Cdouble bond CH2=CH-CH3,propene alkynes -C=C-triple bond H一C=C-CH3,propyne CH,CH, aromatics benzene ring ethylbenzene Copyright 2010 Pearson Prentice Hall,Inc

Hydrocarbons are molecules that are made of carbon and hydrogen ONLY. Hydrocarbons

Common Alkyl Groups One carbon Two carbons Three carbons CH3 CH3- CH3一CH2 CH3一CH2一CH2 CH3-CH- methyl group ethyl group propyl group isopropyl group (or"n-propyl group") Four carbons CH3 CH3 CH3 CH3-CH2一CH2-CH2- CH3-CH-CH2- CH3-CH2-CH- CH3-C- butyl group isobutyl group sec-butyl group (or"n-butyl group") CH3 tert-butyl group (or“t-butyl group") Copyright 2010 Pearson Prentice Hall,Inc

Common Alkyl Groups

CH: CH,CH-CH, CH,一CH-CH CH-CH-CH,CH; CH一CHCH,CH, CH3 CH-CH: CH, CH-CH3 CH: CH: correct seven-carbon chain,but only three substituents seven-carbon chain,four substituents Copyright2010 Pearson Prentice Hall,Inc

Solved Problem 4-1 Give a systematic (IUPAC)name for the following compound. The longest carbon chain contains eight carbon atoms,so this compound is named as an octane.Numbering from left to right gives the first branch on C2;numbering from right to left gives the first branch on C3,so we number from left to riaht. CH 8 CH一CH CH,CH, C CH,- ECH-4CH-CH,-CH-CH3 3 CH. CH CH Copyright2010 Pearson Prentice Hall,Inc 4-isopropyl-2,2,3,6-tetramethyloctane

The longest carbon chain contains eight carbon atoms, so this compound is named as an octane. Numbering from left to right gives the first branch on C2; numbering from right to left gives the first branch on C3, so we number from left to right. Solved Problem 4-1 4-isopropyl-2,2,3,6-tetramethyloctane Give a systematic (IUPAC) name for the following compound

SEC 1 Physical Properties Solubility:hydrophobic Density:less than 1 g/mL Boiling points increase with increasing carbons (little less for branched chains). Melting points increase with increasing carbons (less for odd-number of carbons)

SEC 1 Physical Properties ◼Solubility: hydrophobic ◼Density: less than 1 g/mL ◼Boiling points increase with increasing carbons (little less for branched chains). ◼Melting points increase with increasing carbons (less for odd-number of carbons)

自秋不转大对 Boiling Points of Alkanes ■ Branched alkanes have less surface area contact,so weaker intermolecular forces. 400 300 CH3-(CH2)n-CH3 ()uod 3u!oq 200 n-alkanes 100 0 CH-(CH2)CH3 100 isoalkanes CH3 -200 5 10 15 20 number of carbon atoms

Boiling Points of Alkanes ◼Branched alkanes have less surface area contact, so weaker intermolecular forces

自秋不特大对 Melting Points of Alkanes Branched alkanes pack more efficiently into a crystalline structure,so have higher m.p. 50 偶 even numbers -50 -100 odd numbers -150 奇 -200 0 5 10 15 20 number of carbon atoms

Melting Points of Alkanes ◼Branched alkanes pack more efficiently into a crystalline structure, so have higher m.p. 偶 奇

自秋东精秋对 Branched Alkanes Lower b.p.with increased branching Higher m.p.with increased branching ■Examples: CH3 CH3-C-CH2-CH3 CH3~CH-CH2-CH2-CHs CH3 CH3 CHCH CH3 CH3 bp60°C CH3 CH3 bp58°C bp50°C mp-154°C mp-135°C mp-98°C

Branched Alkanes ◼Lower b.p. with increased branching ◼Higher m.p. with increased branching ◼Examples: H CH3 CH CH3 CH2 CH2 CH3 bp 60°C mp -154°C CH3 CH CH3 CH CH3 CH3 bp 58°C mp -135°C bp 50°C mp -98°C CH3 C C 3 CH3 CH2 CH3