Two compounds are isomers if they have the same chemical formula but a different arrangement of atoms. Use Table 8.4 to ΔH estimate for each of the following gas-phase iso-merization reactions, and indicate which isomer has the lower enthalpy:

a.

b.

c.

d.

TABLE 8.4 Average Bond Enthalpies (kJ/mol) Single Bonds C H - C -N _o C F C CI C Br 391 163 201 272 O-Cl 203 200 243 463 146 190 413 348 293 358 485 328 276 240 259 N-H 155 O-O OF CI-F CI-CI 253 N-F N-CI N Br 242 O-I 234 237 218 193 S H Br-Cl 436 SF 567 431 366 299 339 327 253 218 266 S-Cl S Br S-S C S HF H-Cl H -Br H-I I-CI I-Br 208 175 151 Si-H Si Si Si-C Si- Si Cl 323 226 301 368 464 Multiple Bonds 614 839 615 891 799 1072 495 418 941 607 S O 523 418 C N C O H-C-C-OHH Ethanol Dimethyl ether H O Ethylene oxide Acetaldehyde C-C Cyclopentene Pentadiene Methyl isocyanide Acetonitrile