14. Ignoring stereochemistry, to the nearest kcal/mole, what is the enthalpy dif
ID: 586846 • Letter: 1
Question
14. Ignoring stereochemistry, to the nearest kcal/mole, what is the enthalpy difference for the overall reaction of 1,3,5-trimethylcyclohexane with chlorine and light.
14. Ignoring stereochemistry, to the nearest kcal/mole, what is the enthalpy difference for the overall reaction of 1,3,5- trimethylcyclohexane with chlorine and light. Bond Disassociation Energies kcal/mole Selectivity Ratios C-H C-F C-CI C-Br C-I X-X H-X 1° 2° 3° 1° 98 107 8168 53 E 38 136 E 11.2 1.4 2° 95 106 8068 53 ci 58 103 ci 14 3° 91 106 79 65 50 Br46 88 Br 1 80 1700 | 36 71 C.-30 d. -33 e. not a.-d. 5 a. -25 b. -28Explanation / Answer
we have substitution reaction where C-H bond is broken and substitted by C-Cl bond
here we have C-H secondary bond broken since its selectivity is 4 and we had 6 secondary hydorgen making its 6 x 4 = 24 , while we had 9 primary hydrogen with selectivity 1 we get 9 x 1 = 9 . We had three tertiary H with selectivity 5 making 3 x 5 = 15 , since 24 is greatest count substitutionhappens at secondary hydrogen
The bonds broken are C-H ( secondary) and Cl2 , bonds formed are C-Cl ( tertiary) and C-Cl
Enthalphy = Bond enegies of bons broken - bond energes of bond formed
= BE ( secondary C-H) + BE ( Cl-Cl) - BE ( C-H) - BE ( C-Cl)
= 95 + 58- 80-103
= - 30 KJ/mol
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