reduction of adehydes

[inaccensa]

A q in Ek asked what product is formed when aldehyes are formed. I know most books state that it forms primary alcohols. However ,when aldehydes react with grignard reagent, it forms secondary alchols, whereas formaldehyde forms primary alchols. NaBH4 will form primary and LiBH4 doesn't react with aldehyde since its too strong. So in short, what is the safe pick? I meant if a question does appear on MCAT, what should I pick?

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[loveoforganic]

I assume you mean LiAlH4? In that case, it most certainly does react with an aldehyde. Why would being too strong a reagent inhibit reaction? At any rate, the MCAT would probably not be ambiguous.

 

[DJtiesto]

LiAlH4 is a very powerful reducing agent while NaBH4 will only reduce aldehydes and ketones to primary alcohols and secondary, respectively.