[vhpk]

I have one problem that needs your help:
Why does LiAlH₄ reduce C=O but not C=C, it only reduces C=C in case of conjugation between C=C and C=O ?
Thank you 

[Smrt guy]

After hydride attack, for carbonyls, the product is a lithium alkoxide.  If it were to attack a non-conjugated double bond, the product would be an alkyl lithium.  In the case of conjugated double bonds, the hydride attack yields a lithium enolate (this is far less basic and far more stable than an alkyl lithium).  Quite simply, LAH reduction of carbonyls and/or conjugated alkenes yields a thermodynamically favored intermediate while reduction of isolated alkenes does not.