What is the formula of the complex Lithium tetrahydroaluminate (III)?

LiAlH₄

The correct answer is option 2. \(LiAlH_4\).

Lithium tetrahydroaluminate (III), often referred to as lithium aluminum hydride or simply LiAlH4, is a crucial compound in organic and inorganic chemistry due to its potent reducing properties. Let's break down its structure and significance:

Composition and Structure:

Lithium (Li): Lithium is a monovalent cation \((Li^+)\) with a +1 charge.

Tetrahydroaluminate \(([AlH_4]^-)\): This is the tetrahydroaluminate anion, consisting of one aluminum atom \((Al)\) bonded to four hydrogen atoms \((H)\). The aluminum in \([AlH_4]^-\) has a formal oxidation state of -1.

Formula and Representation:

The formula \(LiAlH_4\) indicates that there is one lithium ion \((Li^+)\) and one tetrahydroaluminate anion \(([AlH_4]^-)\) per formula unit. The compound is neutral overall, balancing the charge of one \(Li^+\) cation with one \([AlH_4]^-\) anion.

Properties and Applications:

Reduction Agent: \(LiAlH_4\) is widely used as a strong reducing agent in organic chemistry. It can reduce a variety of functional groups such as carbonyl compounds (aldehydes, ketones, carboxylic acids, esters, etc.) to their corresponding alcohols.

Reaction Mechanism: The reduction process involves the donation of hydride ions \(H^-\) from \(LiAlH_4\) to the carbonyl carbon, resulting in the formation of alkoxides and ultimately alcohols after aqueous workup.

Versatility: Due to its versatile reactivity, \(LiAlH_4\) finds applications in both laboratory-scale synthesis and industrial processes where high selectivity and efficiency in reducing reactions are required.

Safety Considerations:

Reactivity: \(LiAlH_4\) is highly reactive and must be handled with care. It reacts violently with water and protic solvents, producing hydrogen gas, which can lead to hazardous situations.

Storage: It is typically stored under an inert atmosphere and handled in anhydrous conditions to prevent accidental reactions.

In summary, \(LiAlH_4\) (Lithium tetrahydroaluminate) is a key compound in chemical synthesis, valued for its potent reducing properties and broad applicability in organic chemistry. Its formula \(LiAlH_4\) accurately represents its composition of one lithium ion and one tetrahydroaluminate anion per formula unit.