Lithium aluminium hydride does not reduce simple alkenes or arenes. Alkynes are reduced only if an alcohol group is nearby. It was observed that the LiAlH4 reduces the double bond in the N-allylamides.

Why can LiAlH4 reduce alkenes?

LiAlH4 is a rather hard nucleophilic reductant (HSAB Principle) which means it reacts with electrophiles, and alkenes are not electrophiles. The main reason is that Al needs to remove its hydride. ... But the carbon bonded to the alcohol cannot take on a hydride.

Can LAH reduce double bonds?

* Lithium aluminium hydride, LAH reagent cannot reduce an isolated non-polar multiple bond like C=C. However, the double or triple bonds in conjugation with the polar multiple bonds can be reduced.