Carbon-carbon bond dissociation energies have been measured for alkanes. Without referring to Table 4.3, identify the alkane in each of the following pairs that has the lower carbon-carbon bond dissociation energy, and explain the reason for your choice.

(a) Propane or 2-methylpropane
(b) 2-Methylpropane or 2,2-dimethylpropane

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Bond Dissociation Energies of Some Representative Compounds* TABLE 4.3 Bond dissociation energy Bond dissociation energy kJ/mol (kcal/mol) Bond kJ/mol (kcal/mol) Bond Diatomic molecules 435 159 242 192 150 (104) (38) (58) (46) (36) 568 431 366 297 (136) (103) Cl-Cl H-Cl (71) Alkanes (88) (85) CH3-H CH3CH2 H CH3CH2CH2- (CH3)2CH-H (CH3)2CHCH2-H 410 (CH3)3CH (104) (98) (98) (95) (98) (91) 435 CH3 CH3 CH3CH2 CH3 368 355 410 397 (CH3)2CH-CH3 351 (CH3)3C CH3 (84) (80) 380 334 Alkyl halides CH3F CH3 CI CH3 Br CH3- CH3CHz- CI CH3CH2CH2-C 451 349 293 234 338 343 (108) (CH3)2CH-F 439 339 284 330 263 (83.5) (CH3)2CH CI (70) (56) (81) (82) (CH3)2CH-Br (CH) C-CI (CH3)3C-Br (68) (79) (63) Water and alcohols HO-H CH30-H CH3 OH 497 426 380 (119) (102) (91) (CH3)2CH-OH (CH3)3C-OH 380 385 380 (91) (92) (91)