Functional Group: Nomenclature of Benzene Ring.pptx

Functional Group: Nomenclature of Benzene Ring

1. Nomenclature of BENZENE RING FC 105 Organic Chemistry

2. Benzene Ring An aromatic functional group characterized by a ring of six (6) carbon atoms , bonded by alternating single and double bonds. General Formula:   C C C C C C H H H H H H

3. Monosubstituted Derivatives

4. Monosubstituted Derivatives of Benzene M any monosubstituted derivatives of benzene are named systematically by adding the  name of the substituent to “benzene” which is the parent .

5. Monosubstituted Derivatives of Benzene If the substituent is an alkyl chain with more carbon atoms than benzene , then benzene can be treated as a substituent .

6. Monosubstituted Derivatives of Benzene There are also monosubstituted benzene rings that have  common names . And when naming an aromatic compound with one of these rings,  you need to use the common name as the parent and not the “benzene” .

7. Disubstituted Derivatives

8. Disubstituted Derivatives of Benzene Some disubstituted benzene rings also have common names, and the first thing here is to know the relative positions of  ortho ,  meta ,  and  para: Ortho (o) – next to each other Meta (m) – separated by one carbon Para (p) – across from each other

9. Disubstituted Derivatives of Benzene Xylene is unique in that it actually exists in three different forms or isomers: ortho-xylene, meta-xylene, and para-xylene, distinguished by the different arrangements of the two methyl (-CH 3 ) groups attached to the six-carbon benzene ring.

10. Disubstituted Derivatives of Benzene If any do appear then the compound is not named as a benzene but with a different parent name . These compounds are named as such: Position prefix-Name of the substituent + Name of parent chain

11. Disubstituted Derivatives of Benzene T he compound can also be named as such: Position prefix-Names of the substituents in alphabetical order + benzene Remember if two of the same substituent appears then the prefix di- is used before the substituent's name.

12. Disubstituted Derivatives of Benzene Cresol is an organic compound that refers to methylphenols occurring in three isomers: o-cresol, m-cresol, and p-cresol.

13. Disubstituted Derivatives of Benzene For the other rings with common names, start numbering the ring from the substituent that is part of the common ring such that the other groups get the smallest possible locants:

14. Disubstituted Derivatives of Benzene Using “benzene” as the parent can also be encountered, even though it is not what you’d commonly see:

15. Disubstituted Derivatives of Benzene Number the ring to give the substituents the smallest possible number. If the numbering does not make a difference, then give a smaller locant to the alphabetical priority:

16. Benzenes with three or more Substituents

17. Benzenes with three or more s ubstituents When three or more substituents are present the ortho, meta, para positional prefixes become inadequate and a numbering system for the ring must be applied. Number the ring to give the substituents the smallest possible number.

18. Benzenes with three or more s ubstituents If a substituent from mono-substituted benzenes (Benzene Derivatives) is present, it is given the parent-name in the nomenclature. Also, this substituent is given position one in the numbering system. * The other substituents are numbered such that they get the lowest possible sum. In the compound's name the substituents are given their position number and listed alphabetically. Remember that di-, tri, tetra- prefixes are still used to indicate multiple of the same substituent being present but are ignored for alphabetical listing.

19. Benzenes with three or more s ubstituents T he benzene ring is name in the same fashion as cycloalkanes. The lowest possible number is given to the substituents present. Which ever iteration provides the lowest overall sum of numbers will be used in the compound's name. The substituents are assigned a location number, listed alphabetically and the suffix -benzene is added.

20. Benzenes with three or more s ubstituents What if two common names are possible ?   For example, phenol and aniline, we need to go based on the  priority of the groups . In this case, we are comparing the amine and alcohol, and since  OH stands above NH 2  in the priority chart , the parent chain should be an alcohol (phenol) rather than aniline.

21. Functional Group Priorities for Naming Organic Compounds

22. Functional Group Priorities for Naming Organic Compounds

23. Thank you! Sources: LibreTexts Chemistry Chemistry Steps LLC