JNTU B.Pharmacy I PHARMACEUTICAL ORGANIC CHEMISTRY - I Previous Question Paper (September/October-2021 - R17)

Organic compounds are broadly classified based on the arrangement of carbon atoms in their molecular structure into two main categories: Acyclic (Open-chain) and Cyclic (Closed-chain) compounds.

1. Acyclic or Open-chain compounds (Aliphatic): These compounds contain carbon atoms linked in straight or branched chains. They are further divided into:

• Saturated: Contain only carbon-carbon single bonds (e.g., Alkanes).
• Unsaturated: Contain at least one carbon-carbon double or triple bond (e.g., Alkenes, Alkynes).

2. Cyclic or Closed-chain compounds: These contain at least one ring of atoms. They are classified as:

• Homocyclic (Carbocyclic): The ring consists only of carbon atoms. These are further divided into Alicyclic (non-aromatic) and Aromatic (compounds containing a benzene ring or following Hückel's rule).
• Heterocyclic: The ring contains at least one atom other than carbon (heteroatom), such as Nitrogen, Oxygen, or Sulfur (e.g., Furan, Pyridine).

i) Aldehydes:

Common names are derived from the common name of the corresponding carboxylic acid by replacing the suffix '-ic acid' with '-aldehyde'. For example, HCHO is Formaldehyde and CH3CHO is Acetaldehyde.

In the IUPAC system, the suffix '-e' of the corresponding alkane is replaced by '-al'. The aldehyde carbon is always numbered as C-1. For example, Methanal (HCHO) and Ethanal (CH3CHO).

ii) Carboxylic acids:

Common names are often based on the natural source from which the acid was first isolated. Examples include Formic acid (from ants, Latin: formica) and Acetic acid (from vinegar, Latin: acetum).

In the IUPAC system, the suffix '-e' of the corresponding alkane is replaced by '-oic acid'. The carboxyl carbon is assigned the number 1. For example, Methanoic acid (HCOOH) and Ethanoic acid (CH3COOH). If the acid is attached to a ring, the suffix 'carboxylic acid' is added to the name of the cycloalkane.