Question

Draw structures corresponding to the following IUPAC names: (a) cis-Cyclohexane-1,2-dicarboxylic acid (b) Heptanedioic acid (c) Hex-2-en-4-ynoic acid (d) 4-Ethyl-2-propyloctanoic acid (e) 3-Chlorophthalic acid (f) Triphenylacetic acid (g) Cyclobut-2-enecarbonitrile (h) \(m\) -Benzovlbenzonitrile

Short answer

Draw structures by decoding IUPAC names, positioning functional groups, ensuring correct stereochemistry, and applying checks for fidelity.

Step-by-step solution

Understanding Names and Identifying Functional Groups

Begin by analyzing each given IUPAC name to identify key functional groups and features. For example, in (a) cis-Cyclohexane-1,2-dicarboxylic acid, the key groups are cyclohexane, carboxylic acid, and 'cis' orientation between groups attached to the ring.

Constructing Basic Structures

Draw the basic structure for each compound by arranging carbon atoms according to the carbon chain or ring structure mentioned in the name. For (a), draw a cyclohexane ring, and for (b) a heptane chain.

Positioning Functional Groups

Add functional groups to the basic structures at the specified positions. In (a), place the two carboxylic acids (-COOH) on carbons 1 and 2 of the cyclohexane ring. In (b), the -COOH groups are at each end of the heptane chain (as it's a dioic acid).

Applying Stereochemistry

In structures like (a), apply stereochemistry as specified (cis or trans). For (a), orient the two carboxylic groups on adjacent carbons of the ring on the same side of the cyclohexane plane.

Finalizing the Structures with Substituents and Unsaturations

Add any remaining substituents or unsaturations like double or triple bonds as specified. For (d), attach an ethyl group on the 4th carbon and a propyl group on the 2nd carbon of the octane chain. In (c), add a double bond between carbon 2 and 3, and a triple bond between carbon 4 and 5 of the hexanoic acid scaffold.

Cross-check and Verify

Cross-check that the structures match the IUPAC names by reviewing positions of functional groups, stereochemistry, and substituents. Ensure there are no misplacements or omissions such as missing hydrogen atoms, or unsaturations.

Key concepts

IUPAC Naming

The International Union of Pure and Applied Chemistry (IUPAC) provides a systematic way to name chemical compounds. This ensures uniformity and clarity when referring to different substances across the globe. The IUPAC naming system follows a specific set of rules to assign a unique name to each compound, helping chemists to easily deduce the structure of the compound.

To name an organic molecule, follow these steps:

• Identify the longest carbon chain in the compound. This becomes the parent name, such as 'hexane' for a six-carbon chain.
• Number the chain from the end nearest a substituent or functional group to give the lowest numbers possible in the name.
• Identify and name the substituents or functional groups attached to the main chain. Substituents are named in alphabetical order, with their position numbers prefixed to them.
• Combine these parts together into a single name, using appropriate locants and prefixes to indicate positions and multiplicity of identical groups.
• Final check: Ensure the name adheres to IUPAC's standard conventions and includes all necessary positional indicators.

For instance, a compound named as "4-ethyl-2-propyloctanoic acid" means an octane chain (8 carbons) with an ethyl group on the 4th carbon, a propyl group on the 2nd carbon, and a carboxylic acid functional group.

Functional Groups in Organic Chemistry

Functional groups are specific groupings of atoms within molecules that have their own characteristic properties, regardless of the other atoms in the molecule. These groups are crucial in determining the chemical reactivity and properties of organic molecules.

Some key functional groups you'll encounter include:

• Hydroxyl (-OH): Found in alcohols.
• Carboxyl (-COOH): Found in carboxylic acids like heptanedioic acid.
• Aldehyde (-CHO): Found in compounds like hexanal.
• Keto (C=O): Found in ketones, such as acetone.

Functional groups directly affect the physical and chemical properties of molecules. For example, the carboxyl group (-COOH) is acidic and can donate a hydrogen ion (H+), leading to the molecule behaving like an acid.
Understanding and identifying these functional groups allow chemists to predict the behavior and reactions of organic compounds. It's also a key aspect when drawing molecules based on IUPAC names, as seen in the exercise examples.

Stereochemistry

Stereochemistry deals with the three-dimensional arrangement of atoms in molecules. It is an important concept in organic chemistry because the spatial arrangement can vastly affect a molecule's properties and reactions.

Terms often used in stereochemistry include:

• Cis and Trans: Describes the orientation of functional groups in a molecule relative to a plane of symmetry, often in cyclic structures or alkenes. In "cis-cyclohexane-1,2-dicarboxylic acid," the carboxylic acid groups are on the same side of the cyclohexane ring plane.
• Chirality: Chiral molecules are those that cannot be superimposed on their mirror image, like left and right hands. This can lead to isomers with different biological activities or properties.
• Enantiomers and Diastereomers: Types of stereoisomers where enantiomers are mirror images and diastereomers are not.

Correctly interpreting stereochemistry is critical when working with compounds to ensure the intended properties and reactions are achieved.
For instance, when drawing the structure of a molecule from its IUPAC name, knowing if something is 'cis' or 'trans' helps accurately depict the actual three-dimensional form of the molecule.