Question

Which of the following cannot be obtained from diboranc? (1) \(\mathrm{BII}_{3} \mathrm{CO}\) (2) \(1 \mathrm{I}_{3} \mathrm{BO}_{3}\) (3) \(\mathrm{B}_{2}\left(\mathrm{CII}_{3}\right)_{6}\) (4) \(\mathrm{B}_{2} \mathrm{II}_{6} \mathrm{Na}_{2} \mathrm{IIg}\)

Short answer

Option (4) cannot be obtained from diborane.

Step-by-step solution

- Identify products of diborane reactions

Diborane (B2H6) typically reacts to form compounds such as boranes, borates, and halides of boron. It is important to recognize the typical products of diborane reactions.

- Analyze each option

Evaluate each of the given compounds to determine if it aligns with the known products of diborane reactions. Compare each compound with the known products of diborane.

- Eliminate possible compounds

Eliminate compounds that can be formed through reactions including or involving diborane. Cross-reference each compound with the typical reaction products of diborane.

- Compound-by-compound analysis

(1) \ \(\mathrm{BII}_{3} \mathrm{CO}\): This compound is a halide of boron and CO, which can be formed by diborane reactions.\ (2) \ \(1 \mathrm{I}_{3} \mathrm{BO}_{3}\): This is a borate, which is a common product of diborane reactions.\ (3) \ \(\mathrm{B}_{2}\left(\mathrm{CII}_{3}\right)_{6}\): This compound is an organoborane and can be formed by diborane reactions.\ (4) \ \(\mathrm{B}_{2} \mathrm{II}_{6} \mathrm{Na}_{2} \mathrm{IIg}\): This complex compound contains sodium and magnesium which do not typically combine directly with diborane to form such a compound.

- Determine the incorrect option

Since compound (4) contains elements not typically involved in straightforward diborane reactions, it cannot be obtained from diborane.

Key concepts

Boranes

Boranes are compounds made up of boron and hydrogen. Diborane (B₂H₆) is a well-known example. These compounds exhibit interesting properties due to their electron-deficient nature, making them unique in chemistry.
Boranes are commonly used in organic synthesis, as they can react with alkenes and alkynes to add hydrogen across the double or triple bonds. This process is known as hydroboration.
Furthermore, due to their reactivity, boranes must be handled with caution in laboratory settings.
Some applications of boranes include:

• As reducing agents in chemical reactions.
• In the synthesis of other boron-containing compounds.
• In fuel cells due to their high hydrogen content.

Borates

Borates are compounds that contain boron-oxygen bonds. Unlike boranes, borates are usually more stable and less reactive.
You can often find borates as minerals in the Earth's crust, where they serve important industrial applications.
One of the simplest borates is boric acid (H₃BO₃), which is commonly used as an antiseptic.
Borates are utilized in various industries, such as:

• Glass and ceramics manufacturing, where they help improve thermal and chemical resistance.
• Detergents, providing buffering capacity and acting as a water softener.
• Water treatment, functioning as a mild bacteriostatic.

Organoboranes

Organoboranes are boranes that include organic groups attached to the boron atoms. These compounds are extremely useful in organic synthesis due to their versatility.
One common reaction involving organoboranes is the Suzuki coupling, which is used to form carbon-carbon bonds. This reaction is crucial in the synthesis of pharmaceuticals and complex organic molecules.
Organoboranes also facilitate other valuable reactions, such as:

• Hydroboration-oxidation, converting alkenes to alcohols.
• Reductions, where they act as selective reducing agents.
• Forming polymers used in advanced materials.

Halides of Boron

Halides of boron are compounds where boron is bonded to halogens such as fluorine, chlorine, bromine, or iodine.
These compounds are often volatile and display a range of physical and chemical properties depending on the specific halogen involved.
Boron trihalides like BF₃, BCl₃, and BBr₃ are commonly studied and utilized.
Uses of boron halides include:

• Catalysts in organic reactions due to their strong Lewis acidity.
• As gaseous etchants in semiconductor manufacturing.
• Precursors in the preparation of other boron compounds.