Question

Consider the following reaction to produce methyl acetate: When this reaction is carried out with ${\mathrm{CH}}_3\mathrm{OH}$ containing oxygen-18, the water produced does not contain oxygen-18. Explain.

Short answer

In the esterification reaction between acetic acid (CH3COOH) and methanol with oxygen-18 (CH3^(18)OH) to produce methyl acetate (CH3COOCH3), the oxygen-18 isotope is bonded to the carbon in methanol and is not involved in the formation of water. The water formed results from the reaction between the -OH group from acetic acid and the hydrogen atom (H) from methanol. Thus, the water produced does not contain oxygen-18.

Step-by-step solution

Write the balanced chemical equation

First, we need to write down the balanced equation for the esterification reaction: $C{H}_{3}COOH+C{H}_{3}OH\to C{H}_{3}COOC{H}_3+H_{2}O$

Identify the location of oxygen-18 in methanol

Next, let's identify the location of the oxygen-18 isotope in methanol. The molecule has only one oxygen atom, which is where the oxygen-18 isotope is located. Since this oxygen atom is directly bonded to the carbon, we can denote the oxygen-18 isotope as ${}^{18}\mathrm{O}$, so now the representation of methanol with oxygen-18 is $C{H}_3^{18}OH$.

Consider the formation of methyl acetate

During the esterification reaction, the -OH group from the acetic acid (CH3COOH) and the hydrogen atom (H) from methanol (CH3OH) combine to form water (H2O). Meanwhile, the remaining parts of acetic acid and methanol react together to form methyl acetate. Specifically, the carbonyl oxygen (O) of acetic acid forms a bond with the carbon (C) of methanol, which is in the CH3 group. In the case of methanol with oxygen-18, the reaction is as follows: $C{H}_{3}COOH+C{H}_3^{18}OH\to C{H}_{3}COOC{H}_3+H_2^{18}O$

Explain why the water produced does not contain oxygen-18

Since the oxygen-18 isotope is bonded to the carbon in methanol (CH3OH), it is not involved in the formation of water. The water formed in the reaction results from the reaction between the -OH group from acetic acid (CH3COOH) and the hydrogen atom (H) from methanol (CH3OH). In this case, the oxygen atom in the water is coming from the regular acetic acid, not from the methanol containing the oxygen-18 isotope. Therefore, the water produced in the reaction does not contain oxygen-18.

Key concepts

Oxygen-18 Isotope Tracking

When studying chemical reactions such as esterification, scientists sometimes use isotopic labeling to monitor how atoms move during the reaction.

This is particularly useful with isotopes like oxygen-18, a heavier, non-radioactive form of the typical oxygen atom. By using methanol that contains this isotope, denoted as $C{H}_3^{18}OH$, researchers can track the movement of the oxygen atom through the reaction sequence. The oxygen-18 behaves chemically identical to the more common oxygen-16 isotope but can be distinguished by its mass.

In the esterification reaction, the tracking reveals that the oxygen atom from the methanol (which could be ${}^{18}O$) does not end up in the water byproduct, indicating that it remains in the methyl acetate. Thus, oxygen-18 isotope tracking allows us to understand the path of individual atoms in a reaction, providing insights into the reaction mechanisms.

Methyl Acetate Synthesis

Methyl acetate is a product of the esterification reaction between methanol ($C{H}_{3}OH$) and acetic acid ($C{H}_{3}COOH$).

This reaction can be understood in simple terms: the -OH group from acetic acid combines with the hydrogen from the alcohol group in methanol to form water, while the remaining parts of both molecules join to form methyl acetate ($C{H}_{3}COOC{H}_3$).

Importance in Industry

Methyl acetate is used as a solvent in glues, paints, and nail polish removers, highlighting the practical significance of mastering its synthesis. Moreover, understanding the synthesis process in detail, including the reaction mechanism and the effects of catalysts, is fundamental for optimizing production in industrial settings.

Chemical Equation Balancing

Balancing chemical equations is crucial for accurately representing the conservation of mass in chemical reactions, a fundamental principle in chemistry.

When balancing the equation for the synthesis of methyl acetate, it is essential to ensure that the number of each type of atom on the reactant side equals the number on the product side. In our equation, $C{H}_{3}COOH+C{H}_{3}OH\to C{H}_{3}COOC{H}_3+H_{2}O$, we can confirm that all atoms are balanced:

• 2 carbon atoms
• 6 hydrogen atoms
• 2 oxygen atoms

on both sides of the equation.

Properly balanced equations are vital for predicting the amounts of reactants needed and the amount of products formed, enabling chemists to scale reactions for practical applications, such as industrial manufacturing or laboratory experiments.