Orgo question![destroyer]

[JustwantDDS]

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i dont understand how to do this, the solution is confusing me as well,

step 1 makes an acetylide, right?
step 2 w/CH3, adds the CH3 onto the acetylide, right?
then from here on out i dont get it.............

does the Ch3 MgCl make it act like an acetylide again?
how do u do grignard w/alkynes?!
in which case it attacks the carbonyl of the ketone and then H30 protonates it to an alcohol?

 

[JustwantDDS]

again sorry for crap pic

 

[EpicDentist]

http://forums.studentdoctor.net/showthread.php?t=630578

http://forums.studentdoctor.net/showthread.php?t=428298
http://www.***********.com/showthread.php?3751-Grignard-with-an-alkyne

 

[LaughingGas]

what number is it?

 

[JustwantDDS]

179 in 2008 :-/ old, i know

 

[indigenoustw]

One of the restrictions of Grignard reagents is to avoid preparing it from reagents with acidic hydrogens (avoid acid-base reaction). I would say your thinking is right because the only case I would think otherwise is when a nitrile react with Grignard to produce ketones, in which Grignard acts like a nucleophile and not a base.

Alkyne's pKa is about 25, pretty acidic for it to be deprotonated by Grignard. And the way this question sets up led me to think that a nucleophile should be acquired after step three since step four is a ketone, while could undergo nucleophilic addition to the carbonyl.

I didn't use destroyer so I don't have the answers with me, but I think your thinking is correct.