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GCE-AS-A2-IB Advanced Level Organic Chemistry Revision Notes on the Structure and Nomenclature-naming of Aromatic Compounds Allow time for pictures-graphic images to load * EMAIL query?comment KEYWORDS: fast track to nomenclature examples of ... Hydrocarbons (Arenes) ... Halo-Aromatics ... Phenols ... Aldehydes and Ketones ... Carboxylic Acids and Derivatives ... Amines (prim/sec/tert) ... Amides ... Diazonium Salts and azo dyes ... Nitro-Aromatics ... Sulphonic Acids * TYPE IN NAME AROMATIC QUIZ * organic chemical id tests * Summary of FUNCTIONAL GROUPS and please note that some 'old' names are quoted in () though their use should be avoided if possible, however, many are still used - just put one into GOGGLE! See ALKANES page for comparison with aliphatic and alicyclic compounds Aromatic Hydrocarbons (Arenes) benzene C6H6,
methylbenzene (toluene) C7H8, C6H5CH3
ethylbenzene
phenylethene
('styrene'), the C6H5- aromatic ring grouping is called a phenyl group when quoted as a substituent prefix. So phenylethene is named as a derivative of ethene.
1,2-dimethylbenzene (once called xylenes, ortho, meta and para-xylene)
1-ethyl-2-methylbenzene 1-ethyl-3-methylbenzene
1,2-diethylbenzene
1-methyl-2-propylbenzene 1-methyl-3-propylbenzene 1-methyl-4-propylbenzene
1-ethyl-4-propylbenzene 4-ethyl-1,2-dimethylbenzene:
or aryl halide, aromatic halogen compounds, the halogen is directly attached to the benzene ring.
chlorobenzene
It is not a true aryl halogen compound, the halogen atom is in a non-aromatic side chain, so it is a primary aliphatic halogenoalkane.
are true aryl halides with the halogen attached directly to the benzene ring. These can also be named as 2/3/4-chloro-1-methylbenzene or 2/3/4-chloromethylbenzene They are isomeric with (chloromethyl)benzene above.
2,3-dichloromethylbenzene
If the OH group (hydroxy) is directly attached to a benzene ring, the molecule is classified as a 'phenol'. If not, the molecule is classified as an aliphatic alcohol. This difference is illustrated below with molecules containing a benzene ring (Phenols ROH, R=aryl only)
BUT if the OH is not attached to a benzene ring you get an aliphatic alcohol which is isomeric with an phenols and an ether.
which is isomeric with
methylphenols and the ether,
Aromatic aldehydes and ketones True aromatic aldehydes, R-CHO, have the aldehyde group -CHO directly attached to the ring e.g.
Ketones, R2C=O, are often 'mixed' aliphatic-aromatic in the sense that one R group is alkyl and the other is aryl e.g. 1-phenylethanone (acetophenone, methyl phenyl ketone) Diphenylmethanone (diphenyl
ketone),
Aromatic acids and their derivatives Note: quite a few of the 'old' names are still used and accepted
(primary, 2 H's and only one R group attached to the N of the amine group, R-NH2 where R = alkyl or aryl) The amino (prefix) or amine (suffix) group is directly attached to the aromatic benzene ring e.g. the simplest is C6H5NH2,
phenylamine
2-
or 3-
or 4-chlorophenylamine
1,3-diaminobenzene,
2-methylphenylamine, methyl-2-phenylamine, 1-amino-2-methylbenzene
This is isomeric with
benzylamine
Secondary AROMATIC amines (secondary, one H and two R groups attached to the N of the amine group, R2NH where R = alkyl or aryl) N-methylphenylamine
and diphenylamine
(tertiary, no H and three R groups attached to the N of the amine group, R3N where R = alkyl or aryl) N,N-dimethylphenylamine
and triphenylamine
(primary, no alkyl/aryl R group and 2H's on the N of amide group) The simplest primary aromatic acid amide is
benzamide
or benzenecarboxamide,
(secondary, 1 alkyl/aryl R group and 1H on the N of amide group) N-phenylethanamide, N-methylbenzamide,
Are secondary amides formed in a condensation reaction between a carboxylic acid and an amine. Water is eliminated between the two 'monomers' to give the secondary, polyamide (polymer) linkage ... -COOH
+ H2N-
==> -CO-NH- + H2O
KEVLAR is an aromatic polyamide formed from benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene
Tertiary amides would have no H and 2 aryl/alkyl groups on N of amide group. N,N-dimethylbenzamide,
DIAZONIUM SALTS and AZO DYES: Diazonium salts are formed when primary aromatic amines reaction with nitrous acid e.g. C6H5NH2(aq) + HNO2(aq) + H+(aq) ==> C6H5N2+(aq) + 2H2O(l) The diazonium cation has a nitrogen-nitrogen triple bond system directly attached to the benzene ring e.g. (1) (2) (3)
In alkaline solution these diazonium salts couple with phenols and aromatic amines to form azo dyes. These dyes have benzene rings linked with an azo -N=N- bond system e.g. reacting (1) with phenol gives reacting (1) with phenylamine gives reacting (2) with phenol gives reacting (2) with phenylamine gives
These have the nitro -NO2 group directly attached to the ring. On reduction they form primary aromatic amines. nitrobenzene,
1-chloro-2-nitrobenzene
1-methyl-2-nitrobenzene,
These molecules have a strongly mono-basic acidic group -SO2OH directly attached to the benzene ring e.g.
benzenesulphonic acid,
2-, 3- or
4-methylbenzenesulphonic acid, Revision notes for studying revising tutoring teaching Advanced Level GCE AS A2 CHEMISTRY courses in unofficial support the Chemistry in any advanced-subsidiary AQA, Edexcel, OCR, CIE, WJEC, SQA and CCEA (NI) UK or Cambridge/London/Edexcel International and OCR/CIE and International Baccalaureate (IB) examinations. * Copyright © Dr W P Brown 2000-2008 All rights reserved including the revision notes pages, quizzes, worksheets etc. * Doc Brown's Chemistry Clinic * www.docbrown.info/ * |
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