30 ALKANES There is one isomer characterized by an ethyl substituent on a five-carbon chain: H3,)3CH 3-Ethylpentane The remaining isomer has three methyl substituents attached to a four-carbon chain. (CH3)3 CCH(CH3)2 2, 2, 3-Trimethylbutane 2.17 In the course of doing this problem, you will write and name the 17 alkanes that, in addition to oc- tane, CH;(CH2)CH3, comprise the 18 constitutional isomers of C&H (a) The easiest way to attack this part of the exercise is to draw a bond-line depiction of heptane and add a methyl branch to the various positions 2-Methy heptane 3-Methy heptane 4-Methylheptane Other structures bearing a continuous chain of seven carbons would be duplicates of the isomers rather than unique isomers. 5-Methy heptane, " for example, is an incorrect name methy heptane, and"6-methy heptane"is an incorrect name for 2-methy heptane (b Six of the isomers named as derivatives of hexane contain two methyl branches on a continu- ous chain of six carbons Dimethy lhexane 2, 3-Dimethy lhexane 2, 4-Dimethy lhexane ,5-Dimethy lhexane 3, 3-Dimethylhexane 3. 4-Dimethylhexane One isomer bears an ethyl substituent (c) Four isomers are trimethyl-substituted derivatives of pentane 义人 .3, 3-Trimethylpentane 2. 2. 4-Trimethylpentane Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
There is one isomer characterized by an ethyl substituent on a five-carbon chain: The remaining isomer has three methyl substituents attached to a four-carbon chain. 2.17 In the course of doing this problem, you will write and name the 17 alkanes that, in addition to octane, CH3(CH2)6CH3, comprise the 18 constitutional isomers of C8H18. (a) The easiest way to attack this part of the exercise is to draw a bond-line depiction of heptane and add a methyl branch to the various positions. Other structures bearing a continuous chain of seven carbons would be duplicates of these isomers rather than unique isomers. “5-Methylheptane,” for example, is an incorrect name for 3-methylheptane, and “6-methylheptane” is an incorrect name for 2-methylheptane. (b) Six of the isomers named as derivatives of hexane contain two methyl branches on a continuous chain of six carbons. One isomer bears an ethyl substituent: (c) Four isomers are trimethyl-substituted derivatives of pentane: 2,2,3-Trimethylpentane 2,3,3-Trimethylpentane 2,2,4-Trimethylpentane 2,3,4-Trimethylpentane 3-Ethylhexane 2,2-Dimethylhexane 2,3-Dimethylhexane 2,4-Dimethylhexane 2,5-Dimethylhexane 3,3-Dimethylhexane 3,4-Dimethylhexane 2-Methylheptane 3-Methylheptane 4-Methylheptane 2,2,3-Trimethylbutane (CH3)3CCH(CH3)2 3-Ethylpentane (CH3CH2)3CH 30 ALKANES Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
ALKANES 31 Two bear an ethyl group and a methyl group on a continuous chain of five carbons 3-Ethyl-2-methylpentane 3-Ethyl-3-methylpenta (d) Only one isomer is named as a derivative of butane: 2, 2.3.3-Tetramethylbutan 2.18 (a) The longest continuous chain contains nine carbon atoms. Begin the problem by writing and umbering the carbon skeleton of nonane Now add two methyl groups(one to C-2 and the other to C-3)and an isopropyl group(to C-6) to give a structural formula for 6-isopropyl-2, 3-dimethylnonane CH3 CH(CHsh or CH: CHCHCH,CH,CHCH,CH,CH (b) To the carbon skeleton of heptane(seven carbons) add a tert-butyl group to C-4 and a methyl C-3 to giv C(CH3) CHCH.. CHCH (c) An isobutyl group is-CH, CH(CH3). The structure of 4-isobutyl-l, I-dimethylcyclohexane H3C、 CH, CH(CH3)2 H3C (d) A sec-butyl group is CH_CHCH, CH,. sec-Butylcycloheptane has a sec-butyl group on a even-membered ring (e) A cyclobutyl group is a substituent on a five-membered ring in cyclobutylcycloper Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
Two bear an ethyl group and a methyl group on a continuous chain of five carbons: (d) Only one isomer is named as a derivative of butane: 2.18 (a) The longest continuous chain contains nine carbon atoms. Begin the problem by writing and numbering the carbon skeleton of nonane. Now add two methyl groups (one to C-2 and the other to C-3) and an isopropyl group (to C-6) to give a structural formula for 6-isopropyl-2,3-dimethylnonane. (b) To the carbon skeleton of heptane (seven carbons) add a tert-butyl group to C-4 and a methyl group to C-3 to give 4-tert-butyl-3-methylheptane. (c) An isobutyl group is GCH2CH(CH3)2. The structure of 4-isobutyl-1,1-dimethylcyclohexane is as shown. (d) A sec-butyl group is CH3 = CHCH2CH3. sec-Butylcycloheptane has a sec-butyl group on a seven-membered ring. (e) A cyclobutyl group is a substituent on a five-membered ring in cyclobutylcyclopentane. or CH3CHCH2CH3 1 2 6 4 3 5 H3C H3C CH2CH(CH3)2 or or 1 3 2 4 5 7 6 CH3CH2CHCHCH2CH2CH3 C(CH3)3 CH3 or CH3CHCHCH2CH2CHCH2CH2CH3 CH3 CH(CH3)2 CH3 1 3 2 46 8 57 9 1 2 3 4 5 6 8 7 9 2,2,3,3-Tetramethylbutane 3-Ethyl-2-methylpentane 3-Ethyl-3-methylpentane ALKANES 31 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website