* It is a nucleophilic reducing agent, best used to reduce polar multiple bonds like C=O. * LiAlH4 can reduce aldehydes to primary alcohols, ketones to secondary alcohols, carboxylic acids and esters to primary alcohols, amides and nitriles to amines, epoxides to alcohols and lactones to diols.

AlLiH4 is normally used to reduce 1 degree halide, the reason being that during the process of the reaction, Al develops a negative charge. Being a metal it cannot handle the charge and instantly gives out a hydride ion. The fast removal makes the hydride a strong base and a nucleophile, favouring SN2, which works best for 1 degree.

There are certain steric factors responsible for reduction of tertiary halides.

Hope it helps !!!

Why LiAlH4 can't reduce tertiary halides to alkane?

Tertiary halides, which contain a tertiary carbon atom (a carbon atom bonded to three other carbon atoms), are generally resistant to reduction by LiAlH4 to form alkanes. This is due to several factors that hinder the reduction reaction.

1. Steric Hindrance:
Tertiary carbon atoms are highly substituted and surrounded by bulky alkyl groups. The large size of these groups creates significant steric hindrance, making it difficult for LiAlH4 to approach the carbon atom and initiate the reduction reaction. The steric hindrance prevents the hydride ion (H-) from attacking the carbon atom effectively.

2. Stability of the Carbocation Intermediate:
During the reduction process, a carbocation intermediate is formed as a result of the heterolytic cleavage of the carbon-halogen bond. In tertiary halides, the resultant tertiary carbocation is highly stable due to the presence of multiple alkyl groups and the possibility of hyperconjugation. This stability makes it less likely for the carbocation to undergo further reduction and form an alkane.

3. Strong Electron-Withdrawing Groups:
Tertiary halides often contain electron-withdrawing groups, such as carbonyl groups or nitrile groups, attached to the carbon atom adjacent to the halogen. These groups exert an electron-withdrawing effect, making the carbon atom less nucleophilic and less susceptible to reduction. The electron-withdrawing groups stabilize the positive charge on the carbon atom, further hindering the reduction reaction.

4. Reaction Kinetics:
LiAlH4 is a strong reducing agent that reacts rapidly with carbonyl compounds, such as aldehydes and ketones. The reduction reaction with tertiary halides is slower compared to the reaction with carbonyl compounds. This slower reaction rate can be attributed to the factors mentioned above, such as steric hindrance and the stability of the carbocation intermediate.

In summary, the resistance of tertiary halides to reduction by LiAlH4 to form alkanes is primarily due to steric hindrance, the stability of the carbocation intermediate, the presence of strong electron-withdrawing groups, and the slower reaction kinetics. These factors collectively impede the reduction process, making it challenging to convert tertiary halides to alkanes using LiAlH4.