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Branched-Chain Alkanes. Branched-chain means that other elements besides hydrogen may be attached to the carbon hydrocarbon, halogens, oxygen, nitrogen, sulfur, etc. any atom that takes the place of a hydrogen on a parent hydrocarbon is called a substituent , or the branched part.
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Branched-Chain Alkanes • Branched-chain means that other elements besides hydrogen may be attached to the carbon • hydrocarbon, halogens, oxygen, nitrogen, sulfur, etc. • any atom that takes the place of a hydrogen on a parent hydrocarbon is called a substituent, or the branchedpart
Branched-Chain Alkanes • A hydrocarbon substituent is called an alkyl group • use the same prefixes to indicate the number of carbons, but the -ane ending is now -yl • methyl, ethyl, propyl, etc.
Alkyl Groups Branches on carbon chains H H C CH3 methyl H H H H C C CH3CH2 ethyl H H
Branched Alkanes CH3 CH3CHCH3 methyl groups CH3 CH3 CH3CHCH2CHCH3
Steps for naming Branched-Chain Alkanes p.247-248 1. Count the C’s in the longest chain (parent chain) 2. Number parent chain so branches have lowest possible number 3. Name each branch 4. Use prefix for more than one branch on the same carbon 5. Alphabetize branches 6. Use proper punctuation ( - , )
Naming Branched Alkanes CH3 methyl branch CH3CH2CH2CHCH2CH3 6 5 4 3 2 1 Count
Naming Branched Alkanes CH3 methyl branch CH3CH2CH2CHCH2CH3 6 5 4 3 2 1 Count 3-Methylhexane on third C CH3 six carbon chain group
Learning Check A. CH3CH3 CH3CHCH2CHCH3 B. CH3 CH3 CH3CH2CHCH2CCH2CH3 CH3
Solution A. CH3CH3 CH3CHCH2CHCH3 2,4-dimethylpentane B. CH3 CH3 CH3CH2CHCH2CCH2CH3 CH3 3,3,5-trimethylheptane
Branched-Chain Alkanes • From the name, draw the structure: 1. Find the parent, with the -ane 2. Number carbons on parent 3. Identify substituent groups; attach 4. Add remaining hydrogens
Learning Check Write a condensed structure for A. 3,4-dimethylheptane B. 2,2-dimethyloctane
Solution • 3,4-dimethylheptane CH3 CH3CH2CHCHCH2CH2CH3 CH3
Solution • 2,2-dimethyloctane CH3 CH3CCH2CH2CH2CH2CH2CH3 CH3
Learning Check Write a condensed structure for A. 3-ethylpentane B. 2,3,4-trimethylhexane