Question

Write the IUPAC name of $C{H_3}C{H_2}COOH$ :
A. Ethyl formic acid
B. Ethyl carboxylic acid
C. Ethane methanoic acid
D. Propanoic acid

Answer 1

We need to talk about the IUPAC rules for naming organic compounds. IUPAC is universally recognized for chemical nomenclature and terminology.It provides uniform and consistent nomenclature and terminology to organic compounds.As there a number of organic compounds identified,each requires a systemic nomenclature which is given by the IUPAC system.The system names compounds on the basis of the number of carbon atoms and on the presence of functional groups.

Complete step by step answer:
We must have to remember the following are the basic set of rules to be followed while naming any compound under the IUPAC system:
1. Detect whether the given compound is saturated or unsaturated: Saturated organic compounds contain carbons connected by single bonds only and unsaturated compounds contain double or triple bonds. Alkanes are the roots for naming organic compounds. They are a family of saturated hydrocarbons and hence they have the suffix “-ane”. Incase of unsaturated hydrocarbons, the suffix “-ene” is for hydrocarbons having double bonds and “-yne” for triple bonds.
2. Locate the longest continuous carbon chain: This is the parent chain. Depending on the number of carbons in the parent chain, the alkanes are named as methane (one carbon parent chain),ethane,propane,butane,pentane,hexane,heptane, octane, nonane,decane(ten carbon parent chain).
3. Locate the functional groups: The functional groups are carboxylic acid (-COOH), aldehyde (-CHO), ketone (-CO), alcohol (-OH) and amine $(-NH_2)$.The prefix and suffix in the nomenclature of an organic compound containing these functional groups are given in the table below:

Functional group	Prefix	Suffix
Carboxylic acid	Carboxy-	-oic acid (-carboxylic acid)
Aldehyde	Oxo-(formyl)	-al (carbaldehyde)
Ketone	Oxo-	-one
Alcohol	Hydroxy-	-ol
Amine	Amino-	-amine

4. Locate the substituents: Substituents such as methyl(-CH3), ethyl(-CH2CH3),etc present in the compound replace “ane” ending of alkane with “yl”.
5. Number the chain: The parent chain should be numbered in the direction such that the position number of the first substituent is the smaller number. If the first substituents from either end have the same number, then number so that the second substituent has the smaller number.
Let us now name the given compound $C{H_3}C{H_2}COOH$ .
The given compound is saturated, has 3 carbons in its parent chain and has the $- COOH$ group which is the carboxylic acid functional group. Hence we name the compound as Propanoic acid.
Hence,the correct option is option (D).

Note:
We must be noted that the rules for naming organic compounds is a complex and long data depending on the type of organic compound to be named. For example compounds containing halogen have prefixes such as fluoro,chloro,iodo etc based on the halogen present. There is also another set of rules for cyclic compounds or aromatic compounds.