1.

Which of the following statements are correct during halogenation of alkane

Answer»

The yield of the alkyl halide depends upon the bond dissociation energy of the type of C-H bond
The yield of the ALKANE depends upon the number of a particular type of C-H available
The fluoro compounds cannot be prepared because of high bond energy of F-F
Iodo compounds cannot be prepared by this METHOD because the backward reaction is thermodynamically more favourable

Solution :During the HALOGENATION of alkanes the yield depends upon (i) Bond dissociation energy of C-H bond which is (##ERRL_CHM_V02_C21_E03_105_S01##) More easily the bond can be cleaved, greater will be the yield of the corresponding alkyl halide. (reativity factor). `rArr` Choice (a) is correct
(ii)As a chemical reaction TAKES place due to the collision between the molecules or radicals, more is the possibility for a type of collision, more is the possiblity of the yield corresponding to alkyl halide.
Hence, if a type of C-H bond is more in number then one can expect greater number of collision of `X^dot` with the C-H bond and hence greater will be the yield (number factor)
`rArr` Choice (b) is correct.
(iii)During the iodination of alkanes,
`CH_4+I_2 to CH_3-I+HI`
due to low bond energy of HI and C-I, so backward reaction is thermodynamically more favourable Hence , choice (d) is correct .
(IV)During fluorination , H-F is formed , the bond energy of HF is so very high that the exothermicity lead to explosion that is why fluoro compounds are not prepared by this method .
`rArr` Choice (c ) is incorrect.


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