Organic compounds - nomenclature
Answers
The steps for naming an organic compound are:
Identification of the parent hydrocarbon chain. This chain must o 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)
Now, following the above steps:
The parent hydrocarbon chain has 23 carbons. It is called tricosa-.
The functional groups with the highest precedence are the two ketone groups.
The groups are on carbon atoms 3 and 9. As there are two, we write 3,9-dione.
The numbering of the molecule is based on the ketone groups. When numbering from left to right, the ketone groups are numbered 3 and 9. When numbering from right to left, the ketone groups are numbered 15 and 21. 3 is less than 15, therefore the ketones are numbered 3 and 9. The smaller number is always used, not the sum of the constituents numbers.
The side chains are: an ethyl- at carbon 4, an ethyl- at carbon 8, and a butyl- at carbon 12.
Note:The -O-CH3 at carbon atom 15 is not a side chain, but it is a methoxy functional group.
There are two ethyl- groups. They are combined to create, 4,8-diethyl.
The side chains are grouped like this: 12-butyl-4,8-diethyl. (But this is not necessarily the final grouping, as functional groups may be added in between to ensure all groups are listed alphabetically.
Organic compound is a chemical compound containing hydogen and carbon atoms joined with single covalent bonds.
Nomenclature is the naming of these compounds .
The primary and secondary suffix play an important role in Nomenclature.
√ There are three components of an IUPAC name.
1 .root word
2. primary suffix
3. secondary suffix
The root word example meth , eth , but depends on the number of carbon atoms in the compound.
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Primary suffix
Depends upon the present of single,double or triple bonds
A one bonded compound is ended with -ane
A double bonded compound is ended with -ene
A triple bonded compound is ended with -yne
A single bonded organic compound is called alkane
Example : methane , ethane ,propane
A double bonded organic compound is called alkene
Example : ethene , propene [ methene does not exist can you guess why? ]
A triple bonded compound is called alkyne
Example : ethyne , propyne [ methyne does not exist ]
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Secondary suffix
This depends upon the presence of functional groups
Alcohols
They have OH group of atoms . The secondary suffix is -ol .
Examples :
CH 3 - OH is called methanol
CH 3 - C H 2 - OH is called ethanol
Aldehydes
They have a double bond of O and another bond with H .Their secondary suffix is -al
Examples:-
H-CHO is called methanal
H 3 C - CHO is called ethanal
Note that all aldehydes begin from the compound.No aldehyde can be present in the middle of the compound.
Carboxylic acids
They have a double bond of O and another bond with OH .Their secondary suffix is -oic acid
Examples:-
CH 3 - COOH is called methanoic acid
CH3- CH 2 - COOH is called ethanoic acid
Note that all carboxylic acids begin from the compound.No acid can be present in the middle of the compound.
Ketones
Ketones have double bond O only .
This can only be present in the middle unlike aldehydes
Examples:
CH 3- O - CH -3 is propanone or 2-propanone
CH 3 - CO - C 2 H 5 is butanone 2 - butanone
Alkyl halides
Bromo contains Br atoms and Chloro contains Cl atoms
Examples :
CH 3 Cl is choro methane
CH 3 Br is bromo methane