* Advanced Organic Chemistry Revision on the NAMING & STRUCTURE of AROMATIC COMPOUNDS at Doc Brown's
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Doc Brown's Chemistry REVISING ORGANIC CHEMISTRY Notes on the Molecular Structure and Nomenclature-naming of Aromatic Compounds - Arenes and substituted products Examples of displayed formula of aromatic compounds, graphic formula, molecular formula, skeletal formula, structural formula 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 Google! Most names are based on the generic hexagonal 'benzene' ring with modifications to this based on the highest functional group attached to the ring (i.e. a ring substituent replacing a hydrogen) Revision notes for GCE Advanced Subsidiary Level AS Advanced Level A2 IB Revise AQA GCE Chemistry OCR GCE Chemistry Edexcel GCE Chemistry Salters Chemistry CIE Chemistry revising courses for pre-university students (equal to US grade 11 and grade 12 and Honours/honors level courses) 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 QUIZ * Functional Group Tests * Summary of FUNCTIONAL GROUPS * EMAIL query?comment See ALKANES page for comparison with aliphatic and alicyclic compounds The shapes and bond angles of simple molecules - section on bond angles in organic molecules
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:
Halo-arenes - aryl 'halides' or aryl halide, aromatic halogen compounds, the halogen is directly attached to the benzene ring.
chlorobenzene
chloro-2-methylbenzene, chloro-3-methylbenzene and chloro-4-methylbenzene,or 1-chloro-2-methylbenzene, 1-chloro-3-methylbenzene and 1-chloro-4-methylbenzene (old names 0-chlorotoluene, m-chlorotoluene and p-chlorotoluene). These are true aryl halides with the halogen attached directly to the benzene ring and they are isomeric with (chloromethyl)benzene above.
2,3-dichloromethylbenzene
Phenols - aryl hydroxy compounds 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)
Phenols form salts with strong bases e.g. the alkali sodium hydroxide gives ....
which is oxidised to
If the OH is not attached to a benzene ring you get an aliphatic alcohol which is isomeric with a phenols or 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
methyl-2-nitrobenzene, and the two other positional structural isomers
methyl-3-nitrobenzene,
and
methyl-4-nitrobenzene,
3-nitrobenzoic acid,
Sulphonic Acids (sulfonic acids) These molecules have a strongly mono-basic acidic group -SO2OH directly attached to the benzene ring e.g.
benzenesulphonic acid,
2-, 3- or
4-methylbenzenesulfonic acid,
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ALL bond angles 120o, symmetrical hexagonal ring, planar
molecule
and propylbenzene
is named as a derivative of ethene,
,
1,3-dimethylbenzene
,
1,4-dimethylbenzene
and the two other positional structural isomers
and
,
1,3-dipropylbenzene 
and
the two other
positional structural isomers
and
(uses lower numbers than 1-...-3,4-...)
and
1,2 or 1,3 or 1,4-dichlorobenzene 
,
,
chloromethylbenzene,
or
(chloromethyl)benzene (benzyl chloride). 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.
Three positional structural isomers:
and 1-chloro-2,4-dimethylbenzene
phenol.
sodium
phenoxide (old name sodium phenate?)
2-chlorophenol
(o-chlorophenol),
3-methylphenol
(m-methylphenol, meta-cresol)
2-aminophenol,
4-aminophenol
and
2-nitrophenol
3-hydroxybenzoic
acid and
2-hydroxybenzoic
acid
2,5-dichloro-4-methylphenol
or
1,4-dihydroxybenzene
(benzene-1,4-diol, 1,4-benzenediol, 'quinol')
or
2,5-cyclohexadiene-1,4-dione (cycohexa-2,5-diene-1,4-dione, 'p-quinone')
phenylmethanol
(old name 'benzyl alcohol') is a primary aliphatic alcohol
methoxybenzene
(anisole).
1-phenylethanol,
which is isomeric with the ether
ethoxybenzene
(phenetole) and the ethylphenols or dimethylphenols.
or
benzaldehyde,
and 
2-hydroxybenzaldehyde
,
and 
is a completely aromatic ketone.
, 
,
, 
,
benenecarboxylic acid, benzoic acid
, 
,
, 
,
benzenecarbonyl chloride, benzoyl chloride
, 
,
,
,
benzenecarboxamide, benzamide
, 
,
, 
,
methyl benzenecarboxylate, methyl benzoate
methyl
2-hydroxybenzoate
, 
,
, ethyl
benzenecarboxylate, ethyl benzoate
, 
,
, propyl
benzenecarboxylate, propyl benzoate
2
3 or 4-hydroxybenzenecarboxylic acid, 2 3 or 4-hydroxybenzoic acid
2-chlorobenzoic
acid
benzene-1,2-dicarboxylic acid
(or 1,3 or 1,4)
,
3-aminobenzoic acid, 
or
2-aminomethylbenzene
which is a primary aliphatic amine because the amine group
is not directly attached to the ring.
,
N-ethylphenylamine
,
N,N-diethylphenylamine 
,
,
,
N-phenylbenzamide, 
from
phenylamine
from
4-methylphenylamine
from
2-aminobenzoic acid.
;
1,3-dinitrobenzene, 
,
1-chloro-3-nitrobenzene 
,
1-chloro-4-nitrobenzene
or
1-methyl-2-nitrobenzene
(o-nitrotoluene, ortho nitrotoluene)
or
1-methyl-3-nitrobenzene
(m-nitrotoluene, meta nitrotoluene)
or
1-methyl-4-nitrobenzene
(p-nitrotoluene, para nitrotoluene)
(or
benzenesulphonic acid)
, 
,
(or
2-, 3- or
4-methylbenzenesulphonic acid)|
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