Question

Draw structures corresponding to the following names: (a) 3 -Methylbutanal (b) 4 -Chloro-2-pentanone (c) Phenylacetaldehyde (d) cis-3-tert-Butylcyclohexanecarbaldehyde (e) 3 -Methyl-3-butenal (f) 2 -(1-Chloroethyl)-5-methylheptanal

Short answer

Draw each chemical with the correct groups in indicated positions on the chain or ring.

Step-by-step solution

Understanding 3-Methylbutanal

To draw 3-Methylbutanal, identify its structure. The root 'butan' indicates a four-carbon aldehyde chain. The '3-methyl' branch indicates a methyl group (CH₃) attached to the third carbon.

Draw 3-Methylbutanal

Start by drawing a four-carbon chain. Attach an aldehyde group (CHO) to the first carbon and a methyl group (CH₃) to the third carbon from the same end. The IUPAC name implies unbranched positions unless otherwise specified.

Understanding 4-Chloro-2-pentanone

For 4-Chloro-2-pentanone, the root 'pentan' signifies a five-carbon chain, with a ketone (C=O) at position 2. The '4-chloro' indicates chlorine (Cl) is attached to the fourth carbon.

Draw 4-Chloro-2-pentanone

Draw a five-carbon chain. Place a ketone group (C=O) on the second carbon and a chlorine atom (Cl) on the fourth carbon along the chain.

Understanding Phenylacetaldehyde

Phenylacetaldehyde consists of a 'phenyl' group attached to an 'acetaldehyde' (CH₃CHO). The 'phenyl' indicates a benzene ring, and it is attached to the carbon adjacent to the aldehyde group.

Draw Phenylacetaldehyde

Draw a benzene ring. Connect an acetaldehyde group (CH₂CHO) to the benzene ring, forming phenylacetaldehyde.

Understanding cis-3-tert-Butylcyclohexanecarbaldehyde

This structure includes a cyclohexane ring. A tert-butyl group (offering significant bulkiness) is on the third carbon, and the aldehyde group is directly attached to the ring.

Draw cis-3-tert-Butylcyclohexanecarbaldehyde

Draw the cyclohexane ring, place a tert-butyl group on carbon 3; make sure it's cis relative to the aldehyde group. Lastly, attach an aldehyde group directly to the ring.

Understanding 3-Methyl-3-butenal

Identify 'butenal' as a four-carbon aldehyde with a double bond (ene). The methyl on carbon 3 affects the chain branching.

Draw 3-Methyl-3-butenal

Draw a four-carbon chain with a terminal aldehyde group (CHO). Include a methyl group at carbon 3 and place a double bond between carbon 2 and 3.

Understanding 2-(1-Chloroethyl)-5-methylheptanal

This name maps to a heptanal (seven-carbon aldehyde). A 1-chloroethyl substituent is on carbon 2, and a methyl group is on carbon 5 of the main chain.

Draw 2-(1-Chloroethyl)-5-methylheptanal

Draw a seven-carbon chain and attach a terminal aldehyde (CHO). Connect a 1-chloroethyl group to the second carbon and a methyl group to the fifth carbon.

Key concepts

Aldehyde Structures

Aldehydes are organic compounds characterized by the presence of a carbonyl group (C=O) bonded to a hydrogen atom. This functional group typically appears at the end of a carbon chain, giving aldehydes their distinct terminal position. The RCHO formula represents alderhydes, where R is any alkyl or aryl group.

In the exercise, several aldehydes are involved, like 3-Methylbutanal and Phenylacetaldehyde. For 3-Methylbutanal, the aldehyde group is attached at the end of a four-carbon chain, with a methyl group at the third carbon. For Phenylacetaldehyde, the structure includes a benzene ring (phenyl group) directly attached to the acetaldehyde, highlighting the versatility of aldehyde structures.

Key points to remember about aldehydes:

• They are typically named using the suffix '-al.'
• The carbonyl group is always at the terminal end of the chain.
• The placement of any substituents is specified in the IUPAC name.

Ketone Structures

Ketones, another group of carbonyl-containing compounds, differ from aldehydes as the carbonyl group (C=O) in ketones is flanked by carbon atoms, making it more central within the chain. This placement results in ketones having a slightly different nomenclature and reactivity compared to aldehydes.

In our exercise, 4-Chloro-2-pentanone showcases a typical ketone with its carbonyl group positioned at the second carbon of a five-carbon chain. The presence of a chlorine substituent on the fourth carbon illustrates how other elements can introduce further complexity.

Essential aspects of ketones:

• Their names use the suffix '-one.'
• The position of the carbonyl group is numbered and usually located between two carbons.
• Substituents are indicated in the name, specifying their position relative to the carbonyl group.

Cyclohexane Substituents

Cyclohexane, a six-carbon-containing ring, often serves as a backbone in organic compounds, where various substituents can be attached. The unique structure allows different stereochemistry, like cis and trans arrangements, which alter the compound's properties.

In the example of cis-3-tert-Butylcyclohexanecarbaldehyde, a bulky tert-butyl group is attached to the third carbon, creating steric effects. The 'cis' descriptor indicates that both the tert-butyl and aldehyde groups are on the same side of the cyclohexane ring.

Key points about cyclohexane substituents:

• Cis and trans notations describe the relative positioning of substituents.
• Steric hindrance can impact stability and reactivity.
• Substituents' placement heavily influences the ring's three-dimensional shape.

IUPAC Naming System

The International Union of Pure and Applied Chemistry (IUPAC) naming system provides standardized rules to systematically name chemical compounds, essential for clear and precise communication within the scientific community.

The key components of the IUPAC system include:

• Identifying the longest carbon chain or ring that contains the functional group of interest.
• Numbering the carbon atoms to give the lowest possible numbers to substituents and functional groups.
• Using specific suffixes and prefixes to indicate functional groups and side-chain groups.
• Employing descriptors like 'cis' and 'trans' for geometric isomerism.

In the given exercise, every compound's name derives from these principles. For example, 3-Methylbutanal is named by identifying a four-carbon chain with a terminal aldehyde and a methyl group on the third carbon. By following these steps, the proper organization and identification of complex organic structures are made much simpler.