Nomenclature of Organic Compounds

INTRODUCTION:

We all have seen many compounds and most of them are made of carbon, and that's a fact. We might open a new world and a new way to look at the world if we experiment on these compounds, called organic compounds which have carbon in them as a main substituent. Some of the examples of organic compounds are hydrocarbons, manure, dyes, etc. They are given names by the organization IUPAC (International Union of Pure and Applied Chemistry). Let us see how these compounds are named.

HYDROCARBONS:

Hydrocarbons are compounds that are made of just carbon and hydrogen. They are of two types:

1. Saturated hydrocarbons whose bonds are fully occupied, leaving no extra space for extra atoms. They are also called Alkanes and their names end with the suffix -ane. Their main property is that they don't have 𝜋-bonds.
2. Unsaturated hydrocarbons whose bonds are not fully occupied, leaving a few spaces for extra atoms to join. They are of two types namely:
1. Alkenes having a double bond between two carbon atoms. Their names end with the suffix -ene.
2. Alkynes having a triple bond between two carbon atoms. Their names end with the suffix -yne.

The number of carbon atoms in the molecule is shown in numbers, written in words. The words corresponding to the numbers are given below:

1 - un

2 - eth

3 - prop

4 - but

5 - pent

6 - hex

7 - hept

8 - oct

9 - non

10 - dec

These numbers are used as a suffix to represent carbon atoms or the length of the chain.

FUNCTIONAL GROUPS:

Functional groups are the compounds that are fixed onto an organic compound which helps in forming various different compounds. Some of them are dominant over others. The order for the dominance of these groups is given below:

RULES FOR NOMENCLATURE:

The rules to be kept in mind while naming organic compounds are as follows:

1. Alkane nomenclature:
1. Alkanes
1. Find and name the longest continuous carbon chain.
2. Identify and name groups attached to this chain.
3. Number the chain consecutively, starting at the end nearest a substituent group.
4. Designate the location of each substituent group by an appropriate number and name.
5. Assemble the name, listing groups in alphabetical order using the full name (e.g. cyclopropyl before isobutyl). The prefixes di, tri, tetra, etc., used to designate several groups of the same kind, are not considered when alphabetizing.
2. Cycloalkanes
1. For a monosubstituted cycloalkane, the ring supplies the root name (table above), and the substituent group is named as usual. A location number is unnecessary.
2. If the alkyl substituent is large and/or complex, the ring may be named as a substituent group on an alkane.
3. If two different substituents are present on the ring, they are listed in alphabetical order, and the first cited substituent is assigned to carbon #1. The numbering of ring carbons then continues in a direction (clockwise or counter-clockwise) that affords the second substituent the lower possible location number.
4. If several substituents are present on the ring, they are listed in alphabetical order. Location numbers are assigned to the substituents so that one of them is at carbon #1 and the other locations have the lowest possible numbers, counting in either a clockwise or counter-clockwise direction.
5. The name is assembled, listing groups in alphabetical order and giving each group (if there are two or more) a location number. The prefixes di, tri, tetra, etc., used to designate several groups of the same kind, are not considered when alphabetizing.
2. Alkene and Cycloalkene nomenclature
1. The -ene suffix indicates an alkene or cycloalkene.
2. The longest chain chosen for the root name must include both carbon atoms of the double bond.
3. The root chain must be numbered from the end nearest a double bond carbon atom. If the double bond is in the center of the chain, the nearest substituent rule is used to determine the end where numbering starts.
4. The smaller of the two numbers designating the carbon atoms of the double bond is used as the double bond locator. If more than one double bond is present the compound is named as a diene, triene, or equivalent prefix indicating the number of double bonds, and each double bond is assigned a locator number.
5. In cycloalkenes, the double bond carbons are assigned ring locations #1 and #2. Which of the two is #1 may be determined by the nearest substituent rule.
6. Substituent groups containing double bonds are: H2C=CH– Vinyl group; H2C=CH–CH2– Allyl group.
3. Alkyne nomenclature:
1. The yne suffix (ending) indicates an alkyne or cycloalkyne.
2. The longest chain chosen for the root name must include both carbon atoms of the triple bond.
3. The root chain must be numbered from the end nearest a triple bond carbon atom. If the triple bond is in the center of the chain, the nearest substituent rule is used to determine the end where numbering starts.
4. The smaller of the two numbers designating the carbon atoms of the triple bond is used as the triple bond locator.
5. If several multiple bonds are present, each must be assigned a locator number. Double bonds precede triple bonds in the IUPAC name, but the chain is numbered from the end nearest a multiple bond, regardless of its nature.
6. Because the triple bond is linear, it can only be accommodated in rings larger than ten carbons. In simple cycloalkynes, the triple bond carbons are assigned ring locations #1 and #2. Which of the two is #1 may be determined by the nearest substituent rule.
7. Substituent groups containing triple bonds are: HC≡C– Ethynyl group; HC≡C–CH2– Propargyl group.

Reference: https://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/intro1.htm