Question

Write the condensed structural formula for each of the following compounds: (a) 3,3-dichlorobutyraldehyde, (b) methyl phenyl ketone, (c) para-bromobenzoic acid, (d) methyl-trans-2-butenyl ether, (e) \(N, N\) -dimethylbenzamide.

Short answer

(a) \[CH_3CH_2CH(Cl)_2CHO\] (b) \[C_6H_5COCH_3\] (c) \[p-BrC_6H_4COOH\] (d) \[(CH_2=CH-CH_2)_2OCH_3\] (e) \[C_6H_5CON(CH_3)_2\]

Step-by-step solution

(a) 3,3-dichlorobutyraldehyde

1. Identify the main carbon chain: Butyraldehyde has a carbon chain containing 4 carbon atoms with an aldehyde functional group, which is represented as -CHO. 2. Add substituents: There are two chlorine atoms at the 3rd position. Place both of the chloride atoms on the mentioned position. 3. Write the condensed structural formula: \[CH_3CH_2CH(Cl)_2CHO\]

(b) methyl phenyl ketone

1. Identify the main carbon structure: Phenyl ketone has a benzene ring with a ketone functional group, which is represented as C=O. 2. Add substituents: There is a methyl group (CH3) attached to the ketone. 3. Write the condensed structural formula: \[C_6H_5COCH_3\]

(c) para-bromobenzoic acid

1. Identify the main carbon structure: Benzoic acid has a benzene ring with a carboxylic acid functional group (-COOH). 2. Add substituents: There is a bromine atom on the para (opposite) position of the carboxylic acid group in the benzene ring. 3. Write the condensed structural formula: \[p-BrC_6H_4COOH\]

(d) methyl-trans-2-butenyl ether

1. Identify the main carbon chain: A butenyl chain has 4 carbon atoms with a double bond in the second position. 2. Determine the configuration: The trans configuration of the double bond is when the attached groups are on opposite sides of the double bond. 3. Add substituents: There are two substituents - a methyl group (CH3) and an ether group (OCH3) - attached to the first and second carbon atoms. 4. Write the condensed structural formula: \[(CH_2=CH-CH_2)_2OCH_3\]

(e) \(N, N\) -dimethylbenzamide

1. Identify the main carbon structure: Benzamide has a benzene ring with an amide functional group (-CONH2). 2. Add substituents: There are two methyl groups (CH3) attached to the nitrogen atom of the amide group. 3. Write the condensed structural formula: \[C_6H_5CON(CH_3)_2\]

Key concepts

Organic Chemistry Nomenclature

Understanding how to name organic compounds is crucial for students of chemistry, as it provides a framework for communicating complex structures in a systematic and orderly manner. Nomenclature in organic chemistry follows specific rules set forth by the International Union of Pure and Applied Chemistry (IUPAC).

For instance, let's consider the compound 3,3-dichlorobutyraldehyde. The 'butyraldehyde' indicates a four-carbon aldehyde, and the chloro- prefix denotes the presence of chlorine substituents. The numbers 3,3- tell us the exact location of these substituents on the carbon chain. Thus, the name efficiently describes the structure without even seeing its formula. Through a stepwise approach of identifying the main carbon structure, adding functional groups, and placing substituents according to their locations, one can deduce the condensed structural formula, such as \(CH_3CH_2CH(Cl)_2CHO\) for 3,3-dichlorobutyraldehyde.

• The primary step is finding the longest carbon chain and identifying the main functional groups.
• Next, the location of substituents is determined using numbers.
• Finally, additional functional groups are added to the end of the name, in some cases with locants to indicate their position.

Understanding and applying these rules facilitates clear communication among chemists and aids in learning the complex language of organic chemistry.

Structural Isomers

Structural isomers are molecules that have the same molecular formula but differ in the way their atoms are connected. This means that they can possess distinct physical and chemical properties despite having the same number of each type of atom.

Take for example, the isomers of butanol. All isomers have the formula C4H10O, but can be arranged into different structures such as 1-butanol, 2-butanol, isobutanol, and tert-butanol, each with a unique connectivity of atoms. Factors that contribute to isomerism include the length of the carbon chain, the location of functional groups, and the position of double bonds, as seen in the case of methyl-trans-2-butenyl ether (\(CH_2=CH-CH_2)_2OCH_3\), where 'trans' refers to the specific geometric configuration of the double bond.

• Chain isomers arise from variations in the carbon skeleton.
• Positional isomers have functional groups in different locations.
• Geometric isomers differ in the spatial arrangement around a double bond or a ring structure, such as cis- and trans- isomers.

Grasping the concept of isomers broadens the understanding of the diversity and complexity of organic molecules.

Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties and give the compound its chemical reactivity. Different classes of organic compounds are often defined by the functional groups they contain. For example, aldehydes, such as 3,3-dichlorobutyraldehyde (\(CH_3CH_2CH(Cl)_2CHO\)), possess the -CHO functional group.

The presence of a functional group like -CHO, -COOH in carboxylic acids (para-bromobenzoic acid: \(p-BrC_6H_4COOH\)), or -CONH2 in amides (N,N-dimethylbenzamide: \(C_6H_5CON(CH_3)_2\)) defines the compound's reactivity and properties. Furthermore, the location of a functional group can influence the compound's physical properties, such as boiling point and solubility.

• Alcohols are characterized by the hydroxyl group (-OH).
• Ketones have a carbonyl group (C=O) within the carbon chain.
• Ethers contain an oxygen atom connected to two alkyl or aryl groups, like in methyl-trans-2-butenyl ether.

Mastering functional groups helps understand organic reactions and is essential for recognizing the structure-function relationship in organic chemistry.