Lithium aluminium hydride $(\ce{LiAlH4})$ is known for its vast usability as reducing agent since it can reduce almost any organic functional group to alcohols, amines etc. Despite being so versatile, it cannot reduce alkenes or alkynes to alkanes in general cases.

However, some sources say it can indeed reduce $\pi$ bonds to alkanes in a very special case when the alkene/alkyne is in conjugation with an aryl or a carbonyl group. I want to know in what case exactly can $\ce{LiAlH4}$ behave in this way and what exactly cause it to do so.


1 Answer 1


LAH will reduce alkenes and alkynes in the presence of catalytic amounts first-row transition metal halides NiCl2, TiCl3, CoCl2 as reported by Ashby & Lin

  • $\begingroup$ Okay, but can it behave the same without the need to using any other reagent? Like can it reduce a very specific type of alkene? For example, $\text{MnO}_2$ will oxidize only Benzylic or Allylic alcohol? Is something similar possible for reduction of LAH? $\endgroup$
    – Ansh
    Commented Apr 16 at 3:45
  • $\begingroup$ No, it does not hwpi.harvard.edu/files/myers/files/5-reduction.pdf $\endgroup$
    – Waylander
    Commented Apr 16 at 6:48

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