Main Chain CH; CH3- CHCH2 CH3 CH CH2 CH-CH-CH2CH; CH CH CH.CH3 CH; CH-CH; CH CH3 CH, CH3 wrong correct seven-carbon chain,but only three substituents seven-carbon chain,four substituents Copyright2010 Pearson Prentice Hall,Inc. When there are two longest chains of equal length,use the chain with the greatest number of substituents. Chapter 3 11
Chapter 3 11 Main Chain When there are two longest chains of equal length, use the chain with the greatest number of substituents
Common Alkyl Groups One carbon Two carbons Three carbons CH3 CH3- CH3-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 CH3一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. Chapter 3 12
Chapter 3 12 Common Alkyl Groups
Rule 2:Number the Longest Chain. Methyl is closest to this end of the main chain. 2 CH,CH CH- CH2-CH2一CH 3 4 S 6 3-methylhexane Copyright2010 Peason Prentce Hall.Inc Number the longest chain,beginning with the end of the chain nearest a substituent. 3-methylehexane Chapter 3 13
Chapter 3 13 Rule 2: Number the Longest Chain. Methyl is closest to this end of the main chain. Number the longest chain, beginning with the end of the chain nearest a substituent. 3-methylehexane
Rule 3:Alkyl Substituents 2-methyl 4-ethyl CH3 CH2CH3 CH3CHCH2CHCH2CH3 123 45 6 Name the groups attached to the longest chain as alkyl groups. Give the location of each alkyl group by the number of the main chain carbon atom to which it is attached. Write the alkyl groups in alphabetical order regardless of their position on the chain. 4-ethyl-2-methylhexane Chapter 3 14
Chapter 3 14 Rule 3: Alkyl Substituents CH3CHCH2CHCH2CH3 CH3 CH2CH3 • Name the groups attached to the longest chain as alkyl groups. • Give the location of each alkyl group by the number of the main chain carbon atom to which it is attached. • Write the alkyl groups in alphabetical order regardless of their position on the chain. 1 2 3 4 5 6 2-methyl 4-ethyl 4-ethyl-2-methylhexane
Organizing Multiple Groups When two or more of the same substituents are present, use the prefixes di-,tri-,tetra-,etc.to avoid having to name the alkyl group twice. CH3 CH3 CH3CH2CH2CHCH2CHCH2CH2CHCH3 109876 4321 CH3 Three methyl groups at positions 2,5,and 7 2,5,7-trimethyldecane Chapter 3 15
Chapter 3 15 Organizing Multiple Groups • When two or more of the same substituents are present, use the prefixes di-, tri-, tetra-, etc. to avoid having to name the alkyl group twice. CH3CH2CH2CHCH2CHCH2CH2CHCH3 CH3 CH3 CH3 10 9 8 7 6 5 4 3 2 1 Three methyl groups at positions 2, 5, and 7 2,5,7-trimethyldecane