---
title: "Lithium Aluminum Hydride | Inorganic Chemistry II"
description: "Lithium aluminum hydride (LiAlH4) is a strong hydride reducing agent in Inorganic Chemistry II, used to turn carbonyls, esters, and acids into alcohols."
canonical: "https://fiveable.me/inorganic-chemistry-ii/key-terms/lithium-aluminum-hydride"
type: "key-term"
subject: "Inorganic Chemistry II"
unit: "Unit 7"
---

# Lithium Aluminum Hydride | Inorganic Chemistry II

## Definition

Lithium aluminum hydride (LiAlH4) is a very strong hydride donor used as a reducing agent in Inorganic Chemistry II. It reduces many carbonyl compounds, especially esters and carboxylic acids, to alcohols.

## What It Is

Lithium aluminum hydride, written LiAlH4, is a powerful hydride donor used in Inorganic Chemistry II when you need to reduce a functional group that is not easy to reduce with weaker reagents. It is one of the standard examples of a metal hydride reagent, meaning the useful part of the molecule is the H- transfer it can deliver during a reduction.

The core idea is simple: LiAlH4 gives hydride to an electron-poor carbon, most often the carbonyl carbon in a C=O group. That hydride addition breaks the carbonyl's pi bond and moves the molecule one step closer to an alcohol. Because the reagent is so reactive, it can reduce aldehydes and ketones easily, and it can also push farther than many other hydride reagents by reducing esters and carboxylic acids all the way to primary alcohols.

In practice, LiAlH4 is handled in dry ether solvents and under inert atmosphere because water and air interfere with it. If moisture is present, the reagent reacts before it can do the chemistry you want. That is why lab procedures usually add the substrate to a suspension of the solid reagent in ether, then follow the reaction with a separate aqueous workup step to protonate the oxygen-containing product and destroy any leftover hydride.

Mechanistically, the aluminum center helps organize the reduction. The hydride transfer does not happen in a loose, free-floating way like a simple classroom sketch might suggest. The carbonyl oxygen can coordinate to aluminum, which makes the carbonyl carbon even more electrophilic and sets up hydride attack. After the first addition, the intermediate is converted through a series of protonation and rearrangement steps until the final reduced product is released.

LiAlH4 shows up most often when the course is comparing reducing agents and asking why one reagent works on a given functional group while another does not. It is stronger than many selective hydride reagents, so it is useful, but it is also less forgiving. That balance between power and reactivity is exactly why it is such a common reference point in inorganic and synthetic chemistry.

## Why It Matters

Lithium aluminum hydride is one of the cleanest ways to show how a reagent choice changes the outcome of a synthesis. In Inorganic Chemistry II, it connects group 13 chemistry, metal hydrides, and reduction chemistry in a single example, so it often appears when the course moves from structure to reactivity.

It also gives you a clear comparison point for understanding why some functional groups reduce easily and others need stronger conditions. If you know LiAlH4 reduces esters and carboxylic acids to primary alcohols, you can predict product structures instead of guessing. That kind of product prediction shows up in problem sets and exam-style synthesis questions.

The reagent also highlights a recurring inorganic theme: bonding controls reactivity. The aluminum-hydride framework is not just a source of hydrogen, it is a compact delivery system for hydride transfer. That makes it a useful bridge between main-group chemistry and reaction mechanism.

Because it is moisture-sensitive and highly reactive, LiAlH4 also teaches lab reasoning. You need to think about solvent choice, atmosphere, and workup, not just the organic transformation itself.

## Connections

### Hydride

LiAlH4 works because it delivers hydride, H-, to an electrophilic carbon. If you understand hydride as a nucleophilic reducing species, the reagent’s behavior makes sense across different substrates. The course often uses this idea to compare strong and weak reductions and to explain why carbonyl carbons are such common targets.

### [Reduction Reactions](/inorganic-chemistry-ii/key-terms/reduction-reactions)

LiAlH4 is a classic example of a reduction reagent, so it is often used to show what reduction means in synthesis, not just in redox bookkeeping. In this context, reduction usually means adding hydrogen or lowering the oxidation state of carbon. That is why carbonyls can become alcohols after LiAlH4 treatment.

### [Aluminum Chloride](/inorganic-chemistry-ii/key-terms/aluminum-chloride)

Aluminum chloride and LiAlH4 both put aluminum in a central chemistry role, but they behave very differently. Aluminum chloride is a Lewis acid used to activate other molecules, while LiAlH4 is a hydride donor used to reduce them. Comparing the two helps you see how the same element can support opposite kinds of reactivity.

### [Aluminum Tetrahydridoborate](/inorganic-chemistry-ii/key-terms/aluminum-tetrahydridoborate)

Aluminum tetrahydridoborate is a closely related aluminum hydride reagent, so it is a natural comparison point for LiAlH4. Both are hydride donors, but their structures and reactivity patterns can differ in selectivity and strength. In problem sets, that comparison helps you decide which reagent is more likely to reduce a given functional group.

## On the AP Exam

A problem set or quiz question usually gives you a substrate and asks for the product after LiAlH4 followed by aqueous workup. Your job is to recognize which functional groups are reduced and whether the product should be a primary alcohol, secondary alcohol, or a compound that stays unchanged. For example, an ester turns into a primary alcohol, while an aldehyde becomes a primary alcohol too, but a simple alkane does nothing. If the question includes reaction conditions, you should also notice that the reagent is moisture-sensitive, so the dry solvent and separate workup are part of the chemistry, not just decoration. In short answer or mechanism questions, you may be asked to explain hydride transfer, carbonyl activation by aluminum, or why the reagent must be handled under inert conditions.

## lithium aluminum hydride vs aluminum tetrahydridoborate

These two are both hydride reducing agents and both contain aluminum, so they are easy to mix up. LiAlH4 is generally the stronger, more aggressive reducer, especially for esters and carboxylic acids. If a question asks which reagent can push a harder reduction, LiAlH4 is usually the better match.

## Key Takeaways

- Lithium aluminum hydride, LiAlH4, is a strong hydride donor used for reductions in Inorganic Chemistry II.
- It most often reduces carbonyl-containing compounds, especially aldehydes, ketones, esters, and carboxylic acids, to alcohols.
- The reagent is moisture-sensitive, so dry ether solvents and inert conditions are part of the normal procedure.
- Mechanistically, the aluminum-hydride framework helps deliver hydride to an electrophilic carbonyl carbon.
- When you see LiAlH4 in a reaction, think product prediction, functional group selectivity, and workup steps.

## FAQs

### What is lithium aluminum hydride in Inorganic Chemistry II?

Lithium aluminum hydride, LiAlH4, is a strong hydride reducing agent used to convert electron-poor functional groups into more reduced products. In this course, it usually comes up as a reagent for turning carbonyl compounds into alcohols.

### What does LiAlH4 reduce?

LiAlH4 reduces many carbonyl derivatives, including aldehydes, ketones, esters, and carboxylic acids. It is strong enough to reduce esters and acids all the way to primary alcohols, which is a common point of comparison with weaker reducers.

### Why is lithium aluminum hydride handled in dry solvent?

LiAlH4 reacts quickly with water, so moisture can destroy the reagent before it does the desired reduction. That is why it is usually used in dry ether and followed by a separate aqueous workup after the hydride transfer is complete.

### Is LiAlH4 the same as aluminum tetrahydridoborate?

No, but they are related hydride reagents and easy to confuse. Both transfer hydride, but LiAlH4 is generally the more aggressive reducer and is the one you associate with stronger reductions like esters and carboxylic acids to alcohols.

## Related Study Guides

- [7.2 Boron and Aluminum Compounds](/inorganic-chemistry-ii/unit-7/boron-aluminum-compounds/study-guide/uP7HKDdbiBZyHTJQ)

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