The longest continuous chain that includes the double bond forms the base name of the alkene, and the chain is numbered in the direction that gives the doubly bonded carbons their lower numbers. The locant(or numerical position) of only one of the dou bly bonded carbons is specified in the name; it is understood that the other doubly bonded carbon must follow in sequence CH2=CHCH,CH3 CH3 CH, CH, CH=CHCH3 1-Butene 2-Hexene not 1. 2-butene) (not 4-hexene) determining the main carbon chain and the direction in which it is numbered sen Carbon-carbon double bonds take precedence over alkyl groups and halogens in CH3CHCH=CH, BrCH,CH,CH, CHCH,CH,CH CH3 CH=CH 6-Bromo-3-propyl-1-hexene longest chain that contains double bond is six carbons) Hydroxyl groups, however, outrank the double bond. Compounds that contain both a double bond and a hydroxyl group use the combined suffix -en+ -ol to signify that both functional groups are present 1-ol HOCH CH,CH CHa (not 2-methyl-2-hexen-6-o1) PROBLEM 5.1 Name each of the following using IUPAC nomenclature (a)(CH3)2C-C(CH3)2 d)CH2=CHCH2 CHCH3 (b)(CH3)3CCH=CH2 e) CH2=CHCH, CHCH SAMPLE SOLUTION (a) The longest continuous chain in this alkene contains four carbon atoms the double bond is between c-2 and c-3, and so it is named as a derivative of 2-butene C CH 2,3-Dimethyl-2-butene Identifying the alkene as a derivative of 2-butene leaves two methyl groups to be accounted for as sub ttached to the main chain this alkene is 23 dimethyl-2-butene (It is so es called tetramethylethylene but that is a com- mon name not an IUPAc We noted in Section 2.10 that the common names of certain frequently encoun- tem. Three alkenyl groups--vinyl, allyl, and isopropenyl-are treated the same at tered alky! groups, such as isopropyl and tert-butyl, are acceptable in the IUPAC sy Back Forward Main MenuToc Study Guide ToC Student o MHHE WebsiteThe longest continuous chain that includes the double bond forms the base name of the alkene, and the chain is numbered in the direction that gives the doubly bonded carbons their lower numbers. The locant (or numerical position) of only one of the dou￾bly bonded carbons is specified in the name; it is understood that the other doubly bonded carbon must follow in sequence. Carbon–carbon double bonds take precedence over alkyl groups and halogens in determining the main carbon chain and the direction in which it is numbered. Hydroxyl groups, however, outrank the double bond. Compounds that contain both a double bond and a hydroxyl group use the combined suffix -en -ol to signify that both functional groups are present. PROBLEM 5.1 Name each of the following using IUPAC nomenclature: (a) (CH3)2CœC(CH3)2 (d) (b) (CH3)3CCHœCH2 (e) (c) (CH3)2CœCHCH2CH2CH3 SAMPLE SOLUTION (a) The longest continuous chain in this alkene contains four carbon atoms. The double bond is between C-2 and C-3, and so it is named as a derivative of 2-butene. Identifying the alkene as a derivative of 2-butene leaves two methyl groups to be accounted for as substituents attached to the main chain. This alkene is 2,3- dimethyl-2-butene. (It is sometimes called tetramethylethylene, but that is a com￾mon name, not an IUPAC name.) We noted in Section 2.10 that the common names of certain frequently encoun￾tered alkyl groups, such as isopropyl and tert-butyl, are acceptable in the IUPAC sys￾tem. Three alkenyl groups—vinyl, allyl, and isopropenyl—are treated the same way. C CH3 CH3 H3C H3C 1 2 3 4 C 2,3-Dimethyl-2-butene CH2œCHCH2CHCH3 W OH CH2œCHCH2CHCH3 W Cl C CH3 HOCH2CH2CH2 CH3 H 123 4 5 6 C 5-Methyl-4-hexen-1-ol (not 2-methyl-2-hexen-6-ol) 4 32 1 CH3CHCHœCH2 W CH3 3-Methyl-1-butene (not 2-methyl-3-butene) 6543 2 1 W CHœCH2 BrCH2CH2CH2CHCH2CH2CH3 6-Bromo-3-propyl-1-hexene (longest chain that contains double bond is six carbons) 1 23 4 CH2œCHCH2CH3 1-Butene (not 1,2-butene) 6 5 4 3 21 CH3CH2CH2CHœCHCH3 2-Hexene (not 4-hexene) 5.1 Alkene Nomenclature 169 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website