Advices For Studying Organic Chemistry

Figure 4.9 Heats of combustion show that isobutene is more stable than butane by
9 kJ mol–1.

4.10B HEATS OF COMBUSTION OF CYCLOALKANES

(CH 2 )n + 23 n O 2 n CO 2 + n H 2 O + heat

Table 4.6 Heats of Combustion and ring Strain of Cycloalkanes

Cycloalkane (CH 2 )n n

Heat of

Combustion

(kJ mol–1)

Heat of Combustion

per CH 2 Group

(kJ mol–1)

Ring Strain

(kJ mol–1)

Cyclopropane 3 2091 697.0 (166.59)a 115 (27.49)a

Cyclobutane (^4 2744) 686.0 (163.96)a 109 (26.05)a
Cyclopentane 5 3320 664.0 (158.70)a 27 (6.45)a
Cyclohexane 6 3952 658.7 (157.43)a 0 (0)a
Cycloheptane 7 4637 662.4 (158.32)a 27 (6.45)a
Cyclooctane 8 5310 663.8 (158.65)a 42 (10.04)a
Cyclononane 9 5981 664.6 (158.84)a 54 (12.91)a
Cyclodecane 10 6636 663.6 (158.60)a 50 (11.95)a
Cyclopentadecane 15 9885 659.0 (157.50)a 6 (1.43)a
Unbranched alkane 658.6 (157.39)a –––
a. In kcal mol–1.