Question

what is the Keq for the reaction between methtlmagnesium bromide and
...
a) ammonia
b) ethene

Answer 1

Solution:

A) The reaction between NH3 and CH3MgBr is a simple proton transfer reaction. The reaction equation can be written as,
CH3MgBr + NH3 = CH4 + Mg (NH2)Br
When the CH3- carbanion collides with an ammonia hydrogen, the hydrogen is transferred from ammonia and reaction will essentially go to completion.

Therefore,

Keq = higher than 1.

Keq > 1.

2) CH3MgBr does not reacts with ethene due to less acidic nature of proton in ethene due to sp2 hybridization of double bonded carbons. Thus,

CH3MgBr + CH2=CH2 = No reaction

Therefore,

Keq = always less than 1

Keq < 1