Question

The IUPAC name of cinnamic acid is (a) Phenylpropanoic acid (b) 3-phenylprop-2-enoic acid (c) 3-phenylpropanoic acid (d) Benzene-1, 4 -dicarboxylic acid

Short answer

The IUPAC name of cinnamic acid is 3-phenylprop-2-enoic acid (option b).

Step-by-step solution

Identify the Structure of Cinnamic Acid

Cinnamic acid is an organic compound that comprises a phenyl group (benzene ring) attached to a prop-2-enoic acid chain. This depicts a structure with a benzene ring connected to a three-carbon chain, where the first carbon is part of a carboxylic acid group and the second-to-third carbon forms a double bond (-CH=CH-COOH). This unsaturation in the chain gives the name of the acid a characteristic of a double bond, reflected in the enoic suffix.

Identify the IUPAC Naming Rules for Cinnamic Acid

Under IUPAC nomenclature rules, the carboxylic acid group (-COOH) serves as the principal functional group determining the suffix. The carbon nearest to this group is numbered one, followed by the double-bonded carbon as number two. Thus, the correct IUPAC name of the structure that features a phenyl group substituted at the 3rd position and an alkene bond between the second and third carbon is influenced by these factors. The name should reflect these positions and substitutions accurately according to IUPAC conventions.

Determine the Correct Option

Given the structure and the IUPAC rules, the name needs to specify the phenyl group position and the presence of an alkene. As the phenyl group is on the third carbon, and the presence of a double bond is on the second carbon, the name should begin with '3-phenyl' and include 'prop' for the three carbon atoms. The term 'enoic' denotes the double bond presence, resulting in the full name '3-phenylprop-2-enoic acid.' Option (b) satisfies all these criteria.

Key concepts

Cinnamic Acid Structure

Cinnamic acid is an intriguing organic compound that features a unique structure combining aromatic and aliphatic systems. It is characterized by a benzene ring, often referred to as a phenyl group, linked to a three-carbon aliphatic chain. This chain is termed prop-2-enoic acid, which includes a carboxylic acid functional group (-COOH) at the end.

The presence of a double bond between the second and third carbon elements of this chain is a defining feature. This double bond introduces unsaturation, which means that this carbon chain has less hydrogen than if it were fully saturated. These elements together describe the backbone of cinnamic acid, explaining its physical and chemical behavior.

• Benzene Ring: A stable, six-carbon cyclic feature providing aromatic characteristics.
• Carboxylic Acid Group: Found at the start of the chain, it significantly impacts the molecule's acidity and solubility.
• Double Bond (Alkene Group): Occurring between the second and third carbon atoms in the chain, altering reactivity.

IUPAC Naming Rules

Understanding IUPAC naming is fundamental when it comes to organic chemistry. These rules offer a standardized method to name compounds so that chemists worldwide can communicate effectively. For cinnamic acid, the IUPAC naming starts by identifying the longest carbon chain that includes the primary functional group.

Here are some key IUPAC nomenclature rules to keep in mind for naming organic acids like cinnamic acid:

• Selecting the Main Chain: The longest chain containing the highest priority group, in this case, the carboxylic acid, is chosen.
• Numbering the Chain: Start numbering from the end nearest to the carboxylic group. This ensures the functional groups are given the lowest possible numbers.
• Identifying Substituents: In cinnamic acid, a phenyl group exists as a substituent on the third carbon atom.
• Indicating Double Bonds: The 'enoic' suffix specifies the existence of a double bond in the structure.

Combining all these elements results in the systematic name for cinnamic acid: '3-phenylprop-2-enoic acid.'

Organic Chemistry

Organic chemistry is the study of the structure, properties, composition, reactions, and synthesis of carbon-containing compounds. This field is enormous, covering everything from simple molecules like methane to complex macromolecules like proteins and DNA.

Organic compounds play vital roles in life processes and industrial applications. They form the basis for understanding biological processes, pharmaceutical developments, and innovative materials science. Comprehension of organic chemistry requires familiarity with various concepts and terms, many of which are central to the study of molecules like cinnamic acid.

• Carbon Bonds: Central to the diversity in organic chemistry is the ability of carbon to form four covalent bonds, allowing for functionalities including chains and rings.
• Functional Groups: Specific groupings of atoms like -COOH (carboxylic acid) and -OH (hydroxyl) that confer unique chemical properties.
• Isomerism: The concept that compounds with the same molecular formula can have different structures, greatly influencing physical and chemical properties.

Exploring these principles provides a robust foundation for understanding the varied and intricate nature of organic compounds, such as cinnamic acid.