methylbenzene (toluene) C₇H₈, C₆H₅CH₃

ethylbenzene and propylbenzene

phenylethene ('styrene'), is named as a derivative of ethene,

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 , 1,3-dimethylbenzene, 1,4-dimethylbenzene

(once called xylenes, ortho, meta and para-xylene)

1-ethyl-2-methylbenzene and the two other positional structural isomers

1-ethyl-3-methylbenzene and

1-methyl-2-propylbenzene and the two other positional structural isomers

1-methyl-3-propylbenzeneand

4-ethyl-1,2-dimethylbenzene: (uses lower numbers than 1-...-3,4-...)

Halo-arenes - aryl 'halides'

or aryl halide, aromatic halogen compounds, the halogen is directly attached to the benzene ring.

chlorobenzene 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:

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 and 1-chloro-2,4-dimethylbenzene

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 ....

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

or 1,4-dihydroxybenzene (benzene-1,4-diol, 1,4-benzenediol, 'quinol')

which is oxidised to

or 2,5-cyclohexadiene-1,4-dione (cycohexa-2,5-diene-1,4-dione, 'p-quinone')

If the OH is not attached to a benzene ring you get an aliphatic alcohol which is isomeric with a phenols or an ether.

phenylmethanol (old name 'benzyl alcohol') is a primary aliphatic alcohol

which is isomeric with methylphenols and the ether, methoxybenzene (anisole).

1-phenylethanol, which is  isomeric with the ether

ethoxybenzene (phenetole) and the ethylphenols or dimethylphenols.

True aromatic aldehydes, R-CHO, have the aldehyde group -CHO directly attached to the ring e.g.

orbenzaldehyde, and 2-hydroxybenzaldehyde

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) , and  

Diphenylmethanone (diphenyl ketone), is a completely aromatic ketone.

Primary AROMATIC amines

(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

2-methylphenylamine, methyl-2-phenylamine, 1-amino-2-methylbenzene  or 2-aminomethylbenzene

This is isomeric with benzylamine which is a primary aliphatic amine because the amine group is not directly attached to the ring.

(secondary, one H and two R groups attached to the N of the amine group, R₂NH where R = alkyl or aryl)

and diphenylamine

(tertiary, no H and three R groups attached to the N of the amine group, R₃N where R = alkyl or aryl)

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,

-COOH + H₂N- ==> -CO-NH- + H₂O

Tertiary amides would have no H and 2 aryl/alkyl groups on N of amide group.

e.g. C₆H₅NH₂(aq) + HNO_2(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.

These dyes have benzene rings linked with an azo -N=N- bond system e.g.

methyl-2-nitrobenzene, or 1-methyl-2-nitrobenzene (o-nitrotoluene, ortho nitrotoluene)

and the two other positional structural isomers

methyl-3-nitrobenzene, or 1-methyl-3-nitrobenzene (m-nitrotoluene, meta nitrotoluene)

and

methyl-4-nitrobenzene, or 1-methyl-4-nitrobenzene (p-nitrotoluene, para nitrotoluene)

These molecules have a strongly mono-basic acidic group -SO₂OH directly attached to the benzene ring e.g.

benzenesulphonic acid, (or benzenesulphonic acid)

2-, 3- or 4-methylbenzenesulfonic acid,, , (or 2-, 3- or 4-methylbenzenesulphonic acid)

Website content copyright © Dr W P Brown 2000-2010 All rights reserved on revision notes, puzzles, quizzes, worksheets, x-words etc. * Copying of website material is not permitted * I do not personally endorse the adverts - but they do pay for the site!