5.6 Relative Stabilities of alkenes CH3 CH3 CH3 H CH IGURE 5.4 Heats of com- Alkene CH,=CHCH,CH3 C=CH mers plotted on a common CH3 CH3 scale. All energies are in kilo- joules per mole. (An energy cis-2-Butene equivalent to 0.7 kcal/mol; 7 kJ/mol is equivalent to 1.7 2710 2707 △HP° △H° △H° O 4c02+4H,0 Analogous data for a host of alkenes tell us that the most important factors gov erning alkene stability are 1. Degree of substitution(alkyl substituents stabilize a double bond) 2. Van der Waals strain( destabilizing when alkyl groups are cis to each other) Degree of substitution. We classify double bonds as monosubstituted, disubstituted, trisubstituted, or tetrasubstituted according to the number of carbon atoms that are directly attached to the C=C structural unit. Monosubstituted alkenes RCH=CH as in CH3 CH CH=CH, (1-butene (R and r may be the same or different) RCHECHR CH3 CH=CHCH3 (cis-or trans-2-butene) R (CH3) (2-methy lpr Trisubstituted alkenes (R,R, and r may be the same or different R R as in (CH3)C=CHCH,CH3 (2-methyl-2-pentene) Back Forward Main MenuToc Study Guide ToC Student o MHHE WebsiteAnalogous data for a host of alkenes tell us that the most important factors gov￾erning alkene stability are: 1. Degree of substitution (alkyl substituents stabilize a double bond) 2. Van der Waals strain (destabilizing when alkyl groups are cis to each other) Degree of substitution. We classify double bonds as monosubstituted, disubstituted, trisubstituted, or tetrasubstituted according to the number of carbon atoms that are directly attached to the CœC structural unit. Monosubstituted alkenes: Disubstituted alkenes: (R and R may be the same or different) Trisubstituted alkenes: (R, R, and R may be the same or different) C R R H R C as in (CH3)2C CHCH2CH3 (2-methyl-2-pentene) RCH CHR as in CH3CH CHCH3 (cis- or trans-2-butene) C H R H R C as in (CH3)2C CH2 (2-methylpropene) RCHœCH2 CH3CH2CHœCH2 as in (1-butene) 5.6 Relative Stabilities of Alkenes 177 cis-2-Butene trans-2-Butene Alkene 4CO2 4H2O CH3 6O2 C C H CH3 H 1-Butene 2-Methylpropene 7 7 2710 3 2700 Energy ∆H ∆H ∆H ∆H CH2 CHCH2CH3 CH3 C C H CH3 H CH3 C CH3 CH2 2717 2707 FIGURE 5.4 Heats of com￾bustion of C4H8 alkene iso￾mers plotted on a common scale. All energies are in kilo￾joules per mole. (An energy difference of 3 kJ/mol is equivalent to 0.7 kcal/mol; 7 kJ/mol is equivalent to 1.7 kcal/mol.) Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website