Three moles of B2H6 are completely reacted with methanol. The number of moles of boron containing pr

Q: Why does diborane react so readily with methanol?

Diborane is an electron-deficient molecule, making it a strong Lewis acid. Methanol has an oxygen atom with lone pairs, acting as a Lewis base. The nucleophilic attack by methanol easily cleaves the bridged structure of diborane.

Q: How do I know what the products are?

Reactions of hydrides with protic solvents (like water or alcohols) typically yield hydrogen gas and the corresponding alkoxide/hydroxide derivative. Here, boron forms a stable ester, trimethyl borate $B(OCH_3)_3$.

Q: Is the boron-containing product a solid, liquid, or gas?

Trimethyl borate is a volatile, colorless liquid at room temperature. It is well-known for burning with a distinct green flame.

Q: What if the reaction was with water instead of methanol?

If diborane reacts with water (hydrolysis), the products are boric acid $H_3BO_3$ and hydrogen gas $H_2$. The stoichiometry remains similar: 1 mole of diborane yields 2 moles of boric acid.

Q: Can I just balance the boron atoms to find the answer?

Yes! Since all the boron from diborane ($B_2H_6$) ends up in trimethyl borate ($B(OCH_3)_3$), you can use the principle of atomic conservation. 1 molecule of $B_2H_6$ has 2 boron atoms, so it must form 2 molecules of $B(OCH_3)_3$. Thus, 3 moles will form 6 moles.

Question

Three moles of $	ext{B}_2	ext{H}_6$ are completely reacted with methanol. The number of moles of boron containing product formed is –

Sigma Percentile · Accepted Answer

### The Enigmatic Diborane

Imagine a molecule that defies the standard rules of chemical bonding. That is diborane ($B_2H_6$) for you. It is an electron-deficient molecule, famously known for its "banana bonds" or 3-center-2-electron ($3c-2e$) bonds. Because it lacks sufficient electrons to form standard covalent bonds for all its atoms, diborane acts as a powerful Lewis acid. It is constantly on the lookout for electron-rich species (Lewis bases) to react with and achieve stability.

### The Alcoholysis Reaction

When diborane encounters an alcohol like methanol ($CH_3OH$), a vigorous reaction ensues. The oxygen atom in methanol has lone pairs of electrons, making it an excellent nucleophile. It attacks the electron-deficient boron atoms, effectively cleaving the delicate bridged structure of diborane.

This process, known as alcoholysis, results in the formation of a borate ester and the evolution of hydrogen gas. Specifically, with methanol, the product is **trimethyl borate**, $B(OCH_3)_3$. The balanced chemical equation for this beautiful transformation is:

$$B_2H_6 + 6CH_3OH \longrightarrow 2B(OCH_3)_3 + 6H_2$$

### Stoichiometry: The Heart of the Problem

Now, let's look at the math behind the chemistry. The balanced equation is our roadmap. It tells us the exact stoichiometric ratio between the reactants and the products.

By observing the coefficients, we can clearly see that **$1$ mole of diborane** yields exactly **$2$ moles of trimethyl borate**. This $1:2$ ratio is the key to unlocking the final answer.

### Final Calculation

The problem asks us to find the number of moles of the boron-containing product when $3$ moles of diborane are completely reacted. Using our established stoichiometric ratio, we apply a simple unitary method:

If $1 	ext{ mole of } B_2H_6 \longrightarrow 2 	ext{ moles of } B(OCH_3)_3$

Then, $3 	ext{ moles of } B_2H_6 \longrightarrow 3 	imes 2 = \mathbf{6 	ext{ moles of } B(OCH_3)_3}$

And there we have it! The reaction will produce $6$ moles of trimethyl borate.

### The Ninja Method: Principle of Atomic Conservation (POAC)

What if you blank out during the exam and forget the exact balanced equation? Don't panic. You can solve this using the Principle of Atomic Conservation (POAC) on the Boron atoms.

Since all the boron atoms in the reactant (diborane) must end up in the product (trimethyl borate), we can simply equate the moles of boron atoms on both sides:

$$	ext{Moles of Boron in Reactant} = 	ext{Moles of Boron in Product}$$

$$2 	imes 	ext{Moles of } B_2H_6 = 1 	imes 	ext{Moles of } B(OCH_3)_3$$

$$2 	imes 3 = 1 	imes 	ext{Moles of } B(OCH_3)_3$$

$$	ext{Moles of } B(OCH_3)_3 = \mathbf{6}$$

Boom! You arrive at the exact same answer without needing to balance the entire equation. This is why understanding the core principles is always more powerful than rote memorization.

### Beyond the Problem: The Green Flame Test

As a bonus fact, the trimethyl borate we just formed is not just a random chemical. It is a volatile, colorless liquid that plays a starring role in qualitative analysis. When ignited, trimethyl borate burns with a striking, characteristic **green-edged flame**. This is a classic laboratory test used to confirm the presence of borate radicals in a given salt mixture. Chemistry is not just equations; it's a visual spectacle!

Animated Solution for Chemistry - s and p-Block Elements: Three moles of $B_{2} H_{6}$ are completely reacted with methanol. The number of moles of boron containing product formed is –

Enter Numerical Value:

Visualized Solution

\text{Identifying the Reactants}

\text{The Chemical Reaction}

\text{Stoichiometric Ratio}

\text{Calculation for 3 Moles}

\text{Final Result}

\text{Concept Extension}

The Sigma Insight: Group 13 Elements

The Enigmatic Diborane

The Alcoholysis Reaction

Stoichiometry

Final Calculation

The Ninja Method

Beyond the Problem

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