Problem 14 - General Chemistry

Question

Identify and name the functional group in each of the following. A \(\mathrm{CH}_{3} \mathrm{COCH}_{3}\) B \(\mathrm{CH}_{3} \mathrm{OCH}_{2} \mathrm{CH}_{3}\) C \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2}\) D \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH}\) E \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO}\) F \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\)

Step-by-Step Solution

Answer

A: Ketone, B: Ether, C: Alkene, D: Carboxylic Acid, E: Aldehyde, F: Alcohol.

Step 1: Identify The Functional Group in A

The molecular structure of A is \( \mathrm{CH}_{3} \mathrm{COCH}_{3} \). The central carbon is double-bonded to an oxygen and single bonded to two methyl groups (\( \mathrm{CH}_3 \)). This is characteristic of a ketone functional group.

Step 2: Identify The Functional Group in B

In B, \( \mathrm{CH}_{3} \mathrm{OCH}_{2} \mathrm{CH}_{3} \), the oxygen atom is single-bonded to two alkyl groups: a methyl group and an ethyl group. This structure is typical of an ether functional group.

Step 3: Identify The Functional Group in C

Molecule C, \( \mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2} \), contains a carbon-carbon double bond between the atoms. This is the defining feature of an alkene functional group.

Step 4: Identify The Functional Group in D

In D, \( \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH} \), there is a carbon double-bonded to an oxygen and single-bonded to an -OH group, forming a carboxylic acid functional group.

Step 5: Identify The Functional Group in E

For molecule E, \( \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO} \), the structure includes a terminal carbon double-bonded to an oxygen, forming an aldehyde functional group.

Step 6: Identify The Functional Group in F

In F, \( \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH} \), we see an -OH group attached to an alkyl chain, which is characteristic of an alcohol functional group.

Key Concepts

Ketone Functional Group

A ketone functional group is characterized by the presence of a carbonyl group (C=O) in the middle of a carbon chain. In ketones, the carbonyl carbon is attached to two other carbon atoms. This differs from aldehydes, where the carbonyl carbon is bonded to at least one hydrogen atom. Ketones are important in both industrial and biological processes. For example, acetone, the simplest ketone ( CH 3 C(O)CH 3 ), is used as a solvent. The carbonyl group contributes to the ketone's polarity, making it soluble in water. The presence of two carbon groups makes ketones more stable compared to aldehydes.

Ether Functional Group

The ether functional group consists of an oxygen atom connected to two alkyl or aryl groups. The general structure of an ether is R-O-R', where R and R' represent carbon-containing groups. Ethers can be found in everyday substances such as diethyl ether, which was historically used as a general anesthetic. This functional group's oxygen atom contributes to increased polarity compared to hydrocarbons, although ethers are generally less reactive than alcohols or carbonyl-containing compounds. Ethers play a significant role in organic synthesis and serve as good solvents for reactions due to their stability and inertness.

Alkene Functional Group

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C), which is the hallmark of the alkene functional group. This double bond affects the chemical properties of alkenes, making them more reactive than alkanes. Alkenes are used as starting materials in polymer production, such as the synthesis of polyethylene from ethene. Alkenes undergo characteristic reactions like hydrogenation, hydration, and polymerization. Their unsaturation allows for addition reactions, where new atoms can be added across the double bond.

Carboxylic Acid Functional Group

Carboxylic acids contain a carbonyl group (C=O) and a hydroxyl group (-OH) bonded to the same carbon atom, forming the carboxyl group (-COOH). This combination significantly influences their chemical properties, particularly their acidity. Carboxylic acids release protons in solutions, forming carboxylate anions, which makes them acidic. They are known for their diverse applications, including the production of acetylsalicylic acid (aspirin) and acetic acid, which is a key component of vinegar. Carboxylic acids can participate in reactions such as esterification, where they react with alcohols to form esters, another important functional group.

Aldehyde Functional Group

The aldehyde functional group is characterized by a carbonyl group bonded to at least one hydrogen atom, with the general form R-CHO. Aldehydes are similar to ketones but differ in that the carbonyl group is located at the end of a carbon chain. Aldehydes are crucial in various reactions, including oxidation, to form carboxylic acids, and reductions, to form alcohols. An example is formaldehyde ( CH 2 O ), which is used in the production of plastics and disinfectants. Aldehydes tend to be more reactive than ketones due to the hydrogen attached to the carbonyl carbon, which makes them more accessible to nucleophilic attacks.

Alcohol Functional Group

Alcohols contain one or more hydroxyl groups (-OH) attached to a carbon atom. The presence of the hydroxyl group makes alcohols polar, influencing their solubility in water and their boiling points. Alcohols are versatile in both natural and synthetic chemistry. Ethanol, a simple alcohol, is often found in beverages and used as a solvent and fuel. Alcohols can engage in reactions like oxidation, in which primary alcohols can be converted to aldehydes or carboxylic acids. The hydroxyl group in alcohols can also undergo substitution to form esters or ethers, highlighting their role as intermediates in various chemical syntheses.