explain in detail the nomenclature of carbon compound? 6 marks question
Answers
Most of the carbon compounds have two types of names:
Trivial Names
IUPAC Names
Trivial Names
The trivial names are the commonly used names of carbon compounds. They are derived mostly from the source of the compound e.g., the name of formic acid is derived from 'formicus' the Greek word meaning red ants. Names arrived in this way were ambiguous and repeating.
IUPAC Names
With the large growth of carbon compounds, it was necessary to name these compounds in a more systematic way. A committee called the 'International Union for Pure and Applied Chemistry' (IUPAC) put forward a system of giving proper scientific names to carbon based compounds. The names derived by their rules are the names followed all over the world and in short are called IUPAC names.
In this system the name of a carbon compound has three main parts as mentioned below:
Wood Root
This denotes the number of carbon atoms present in a given molecule. For e.g., C1-Meth, C2- Eth, C3 - Prop, C4- But.
Suffix
The suffix denotes the type of bonds or the functional group present in the carbon chain, e.g.
Type of bondFunctional group
'ane' (single bond)'ol' for alcohols (-OH)'ene' (double bond)'al' for aldehydes (-CHO)'yne' (triple bond)'oic acid' for carboxylic acid (-COOH)
Prefix
This denotes the presence of other functional groups and their position.
For e.g., the following compound can be named as..
Answer:
Explanation:
The steps for naming an organic compound are:
Identification of the parent hydrocarbon chain. This chain must obey the following rules, in order of precedence:
It should have the maximum number of substituents of the suffix functional group. By suffix, it is meant that the parent functional group should have a suffix, unlike halogen substituents. If more than one functional group is present, the one with highest precedence should be used.
It should have the maximum number of multiple bonds.
It should have the maximum number of single bonds.
It should have the maximum length.
Identification of the parent functional group, if any, with the highest order of precedence.
Identification of the side-chains. Side chains are the carbon chains that are not in the parent chain, but are branched off from it.
Identification of the remaining functional groups, if any, and naming them by their ionic prefixes (such as hydroxy for -OH, oxy for =O, oxyalkane for O-R, etc.).
Different side-chains and functional groups will be grouped together in alphabetical order. (The prefixes di-, tri-, etc. are not taken into consideration for grouping alphabetically. For example, ethyl comes before dihydroxy or dimethyl, as the "e" in "ethyl" precedes the "h" in "dihydroxy" and the "m" in "dimethyl" alphabetically. The "di" is not considered in either case). When both side chains and secondary functional groups are present, they should be written mixed together in one group rather than in two separate groups.
Identification of double/triple bonds.
Numbering of the chain. This is done by first numbering the chain in both directions (left to right and right to left), and then choosing the numbering which follows these rules, in order of precedence
Has the lowest-numbered locant (or locants) for the suffix functional group. Locants are the numbers on the carbons to which the substituent is directly attached.
Has the lowest-numbered locants for multiple bonds (The locant of a multiple bond is the number of the adjacent carbon with a lower number).
Has the lowest-numbered locants for prefixes.
Numbering of the various substituents and bonds with their locants. If there is more than one of the same type of substituent/double bond, a prefix is added showing how many there are ( di – 2 tri – 3 tetra – 4 then as for the number of carbons below with 'a' added)
The numbers for that type of side chain will be grouped in ascending order and written before the name of the side-chain. If there are two side-chains with the same alpha carbon, the number will be written twice. Example: 2,2,3-trimethyl- . If there are both double bonds and triple bonds, "en" (double bond) is written before "yne" (triple bond). When the main functional group is a terminal functional group (a group which can exist only at the end of a chain, like formyl and carboxyl groups), there is no need to number it.
Arrangement in this form: Group of side chains and secondary functional groups with numbers made in step 3 + prefix of parent hydrocarbon chain (eth, meth) + double/triple bonds with numbers (or "ane") + primary functional group suffix with numbers.
Wherever it says "with numbers", it is understood that between the word and the numbers, the prefix(di-, tri-) is used.
Adding of punctuation:
Commas are put between numbers (2 5 5 becomes 2,5,5)
Hyphens are put between a number and a letter (2 5 5 trimethylheptane becomes 2,5,5-trimethylheptane)
Successive words are merged into one word (trimethyl heptane becomes trimethylheptane)
Note: IUPAC uses one-word names throughout. This is why all parts are connected.
The finalized name should look like this:
#,#-di<side chain>-#-<secondary functional group>-#-<side chain>-#,#,#-tri<secondary functional group><parent chain prefix><If all bonds are single bonds, use "ane">-#,#-di<double bonds>-#-<triple bonds>-#-<primary functional group>
Note: # is used for a number. The group secondary functional groups and side chains may not look the same as shown here, as the side chains and secondary functional groups are arranged alphabetically. The di- and tri- have been used just to show their usage. (di- after #,#, tri- after #,#,#, etc.)