Question

Methyl acetate \(\left(\mathrm{CH}_{3} \mathrm{COOCH}_{3}\right)\) is formed by the reaction of acetic acid with methyl alcohol. If the methyl alcohol is labeled with oxygen-18, the oxygen-18 ends up in the methyl acetate: (a) Do the \(\mathrm{C}-\mathrm{OH}\) bond of the acid and the \(\mathrm{O}-\mathrm{H}\) bond of the alcohol break in the reaction, or do the \(\mathrm{O}-\mathrm{H}\) bond of the acid and the \(\mathrm{C}-\mathrm{OH}\) bond of the alcohol break? (b) Imagine a similar experiment using the radioisotope \({ }^{3} \mathrm{H}\), which is called tritium and is usually denoted T. Would the reaction between \(\mathrm{CH}_{3} \mathrm{COOH}\) and \(\mathrm{TOCH}_{3}\) provide the same information about which bond is broken as does the above experiment with \(\mathrm{H}^{18} \mathrm{OCH}_{3}\) ?

Short answer

(a) In the formation of methyl acetate (CH3COOCH3), the O-H bond of the acid (CH3COOH) and the C-OH bond of the alcohol (H18OCH3) break. (b) No, the reaction between CH3COOH and TOCH3 does not provide the same information about which bond is broken as the reaction with H18OCH3.

Step-by-step solution

Identify the reactants and the product

The given reaction is the formation of methyl acetate (CH3COOCH3) from acetic acid and methyl alcohol. The reactants and the product are: - Acetic acid: CH3COOH - Methyl alcohol (with oxygen-18): H18OCH3 - Methyl acetate: CH3COOCH3

Determine the components of each compound

Let's analyze each reactant and the product to identify the parts that may be involved in the bond-breaking process: - Acetic acid: Contains a C-OH bond and an O-H bond. - Methyl alcohol: Contains an O-H bond. - Methyl acetate: Contains a C-O bond.

Compare the bonds of reactants and product

Now we will compare the bonds present in the reactants and the product to deduce which bonds break during the reaction. In the reactants, we have: -CH3COOH: C-OH and O-H - H18OCH3: O-H bond In the product, we have: -CH3COOCH3: C-O bond The O-H bond from methyl alcohol is no longer present in methyl acetate, and the C-O bond is now present in methyl acetate. Therefore, the breaking bonds in the reaction are: (a) O-H bond of the acid and the C-OH bond of the alcohol.

Analyze the reaction with tritium instead of oxygen-18

Now we need to evaluate if the reaction between CH3COOH and TOCH3 would provide the same information about which bond breaks as the reaction with H18OCH3. The reactants and the product are now: - Acetic acid: CH3COOH - Methyl alcohol (with tritium): TOCH3 - Methyl acetate: CH3COOCH3

Compare the bonds in the reactants and product for the tritium reaction

Let's compare the bonds present in the reactants and the product for the tritium reaction: In the reactants, we have: -CH3COOH: C-OH and O-H - TOCH3: C-H bond (involving tritium) In the product, we have: -CH3COOCH3: C-O bond Comparing these bonds, it is not possible to determine if the O-H bond of the acid or the C-OH bond of the alcohol breaks during the reaction. (b) No, the reaction between CH3COOH and TOCH3 does not provide the same information about which bond is broken as the reaction with H18OCH3.

Key concepts

Methyl Acetate Formation

Methyl acetate is a type of ester formed through a chemical reaction between acetic acid and methyl alcohol. In simpler terms, it results from combining an acid and an alcohol with the removal of water. During this process, specific bonds in both molecules break and re-form to create a new compound.To focus particularly on the reactants:

• Acetic Acid (\( ext{CH}_3 ext{COOH} \)): Contains carbon-oxygen (-C-OH) and oxygen-hydrogen (-O-H) bonds.
• Methyl Alcohol (\( ext{H}_3 ext{COH} \)): Contains a single oxygen-hydrogen (-O-H) bond.

During the formation of methyl acetate (\( ext{CH}_3 ext{COOCH}_3 \)), these bonds change. The carbon-oxygen bond of the alcohol mixes with a part of the acid to create an ester linkage, and the by-product is water. Understanding these transformations helps chemists design and manipulate organic synthesis processes.

Isotopic Labeling

Isotopic labeling is a technique used in chemistry to track the movements of atoms through a reaction. By substituting a standard atom in a molecule with one of its isotopes, scientists can see how those atoms behave differently during chemical processes. In the case of methyl acetate formation, oxygen-18 is used as a label. With isotopic labeling, the attention is on the specific component that contains the labeled atom. The use of oxygen-18 helps reveal which bonds break and which ones form, as the position of the labeled oxygen indicates the path it followed through the reaction. This method is crucial because it delivers insight into mechanistic details of chemical reactions, aiding in understanding complex organic chemistry processes.

Bond Breaking Analysis

When studying chemical reactions, one of the key considerations is understanding which bonds break and which new bonds form. This information can guide predictions about the behavior and properties of the resulting compounds. In the reaction forming methyl acetate from acetic acid and methyl alcohol, careful analysis shows:

• The oxygen-hydrogen bond (O-H) in the alcohol breaks.
• The carbon-oxygen bond (C-O) forms instead, thanks to the contribution of the OH part from the acid, which merges with the alcohol's methyl group.

This transformation is characteristic of esterification reactions, where an ester bond replaces a combination of alcohol and acid bonds.

Radioisotopes in Chemistry

Radioisotopes, atoms with excessive nuclear energy, are incredibly useful in studying reaction pathways. One of the most common radioisotopes is tritium (\( ^3 ext{H} \)), a heavy isotope of hydrogen.Using tritium substitution in chemical reactions, compared to other isotopes like oxygen-18, offers distinct insights. However, in the context of forming methyl acetate from acetic acid and methyl alcohol, tritium does not directly indicate the breakage of specific bonds, unlike the clear signal provided by the isotopic oxygen label.Despite this limitation, tritium finds extensive use in biological systems and other complex chemical reactions due to its radioactive properties, which can be detected and measured with high precision. This makes it a versatile tool in the chemist's toolkit for unraveling multifaceted chemical adventures.