Question

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

Short answer

(a) \(CH_3CH(Cl)CH_2CHO\), (b) \(PhCOC_2H_5\), (c) \(p-BrC_6H_4COOH\), (d) \(CH_3OCH=CHCH_3\), (e) \(C_6H_5CON(CH_3)_2\)

Step-by-step solution

Identify the main functional group

The main functional group is aldehyde. The parent chain has 4 carbons, thus it is a "butyraldehyde."

Add substituents to the chain

The name "3,3-dichlorobutyraldehyde" tells us that there are two chlorine atoms on the third carbon. So, the condensed structural formula is: \(CH_3CH(Cl)CH_2CHO\). (b) methyl phenyl ketone

Identify the main functional group

The main functional group is a ketone, but it has a phenyl and methyl attached to the carbonyl carbon.

Add substituents to the carbonyl

The condensed structural formula for methyl phenyl ketone is: \(C_6H_5COC_2H_5\) or \(PhCOC_2H_5\) (Ph is a common abbreviation for the phenyl group). (c) para-bromobenzoic acid

Identify the main functional group

The main functional group is a carboxylic acid, and it is attached to a benzene ring.

Determine the position of the bromine atom

"para" means that the bromine is located on the opposite position to the carboxylic acid on the benzene ring. The condensed structural formula is: \(p-BrC_6H_4COOH\). (d) methyl-trans-2-butenyl ether

Identify the main functional group

The main functional group is ether, with a trans-2-butenyl and a methyl group attached.

Draw the structure

In the structure of 2-butenyl, carbon 2 has a double bond. The "trans" indicates that when the structure is drawn, one hydrogen atom is on the opposite side of carbon 2 as the ether group. The condensed structural formula for methyl-trans-2-butenyl ether is: \(CH_3OCH=CHCH_3\). (e) \(N, N\) -dimethylbenzamide

Identify the main functional group

The main functional group is an amide, with a benzene ring as the parent.

Add substituents

\(N, N\)-dimethyl indicates that there are two methyl groups on the nitrogen of the amide group. The condensed structural formula for \(N, N\)-dimethylbenzamide is: \(C_6H_5CON(CH_3)_2\).

Key concepts

Organic Chemistry Nomenclature

Understanding the language of chemistry, specifically organic chemistry nomenclature, is fundamental for students to interpret and communicate the structures of organic compounds effectively.

Organic nomenclature involves a systematic method of naming compounds based on the International Union of Pure and Applied Chemistry (IUPAC) rules. These rules dictate that the name of an organic compound reflects its structure, providing insights into both the arrangement of atoms and the presence of functional groups.

For example, in the compound 3,3-dichlorobutyraldehyde, the prefix '3,3-dichloro-' informs us that two chlorine atoms are attached to the third carbon in the chain, while 'butyraldehyde' indicates a four-carbon aldehyde. When writing condensed structural formulas, it’s crucial to identify the longest carbon chain, name it, and then add the substituents and their positions as in the given example \(CH_3CH(Cl)CH_2CHO\).

By breaking down the names and converting them to structural formulas, students can better visualize and understand the molecular structure of the compounds they encounter.

Functional Groups in Chemistry

Functional groups are specific groups of atoms within molecules that have characteristic properties and reactivities. These groups are the focal point of the molecule since they largely determine the compound's chemical behavior.

In organic compounds, identifying the main functional group is essential, as it provides a key to the compound's reactivity and how it is named. For instance, in organic compounds like methyl phenyl ketone (\(C_6H_5COC_2H_5\)), the carbonyl group attached to a phenyl and methyl group (\(C=O\)) signifies it as a ketone.

Each functional group has a particular set of naming rules and priorities that affect the compound's name. In the example of para-bromobenzoic acid (\(p-BrC_6H_4COOH\)), 'benzoic acid' alludes to a carboxylic acid (\(-COOH\)) attached to a benzene ring, while 'para' describes the relative position of the bromine substituent. It's important for students to familiarize themselves with various functional groups to navigate organic chemistry’s complex nomenclature effectively.

Isomerism

Isomerism is a concept that describes the phenomenon where compounds with the same molecular formula can have different structures—known as isomers. There are several types of isomerism, such as structural isomerism and stereoisomerism.

Structural isomers differ in how atoms are connected to each other, while stereoisomers have the same bonds but differ in the spatial arrangement of atoms. A common type of stereoisomerism encountered in organic chemistry is geometric (cis-trans) isomerism, which is particularly relevant in compounds with double bonds.

In the compound methyl-trans-2-butenyl ether (\(CH_3OCH=CHCH_3\)), 'trans' indicates that the substituents are on opposite sides of the double bond, affecting the compound's shape and physical properties. Recognizing isomerism is vital in understanding the diversity of organic chemical behaviors and is crucial for advanced topics such as reaction mechanisms and biomolecular functions.