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Which compounds are not useful for preparation of grignard reagents?

a) 4-chlorobut-1-yne
b) 2-chloroethan-1-amine
c) 1-bromobutan-2-ol
d) 4-bromocyclohexan-1-ol

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  • $\begingroup$ What are your thoughts on this? $\endgroup$ – Waylander Jun 20 '18 at 14:43
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    $\begingroup$ Is this a trick question? $\endgroup$ – ringo Jun 20 '18 at 14:49
  • $\begingroup$ @Ringo yes, sort of. The stydent is supposed to find fault with all of them. $\endgroup$ – Oscar Lanzi Feb 20 at 14:04
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Seems to me that there are solid reasons why NONE of the materials will form Grignards unless they are modified.

1 - The alkyne proton (pKa ~25) will quench any Grignard formed to give the Mg salt

2 - The free base is already unstable in solution wrt aziridine formation/polymerisation; any added base promotes this. Any Grignard formed will also be quenched by the NH2 protons.

3- The -OH proton will quench any Grignard forming the alkoxide which is liable to form the epoxide.

4- Similarly the -OH proton will quench any Grignard forming the alkoxide which can then form the tetrahydrofuran

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