P3 Task 1 Explain the chemical properties of industrially important benzene
and monosubstituted benzene compounds
Benzene is known to undergo multiple reactions but the important ones are hydrogenation,
sulfonation, combustion, alkylation, chlorination, and nitration. Hydrogenation is known as
an addition reaction because it forms a cycloalkane this type of reaction helps to destroy the
electron delocalisation in the original benzene ring this is because those same electrons are
used to form bonds with the new hydrogen atoms.(Chemlibretexts.org other Reactions of
Benzene and Methylbenzene, Author unknown 2022)
The next type of reaction benzene can undergo is called sulfonation which involves changing
one of the hydrogens on the benzene ring this is done by the sulfonic acid group. Moreover,
the sulfonation of benzene can be done in two ways the first is heating the benzene under
the reflux with a strong concentrated sulfuric acid for a few hours and the second way is to
warm the benzene under reflux at a temperature of 40°C along with the sulfuric acid this
should be done for no more than 20 to 30 minutes.(Chemlibretexts.org other Reactions of
Benzene and Methylbenzene, Author unknown 2022)
Benzene undergoes combustion because it needs to burn plenty of oxygen to give out
carbon dioxide and water but combustion is not always complete particularly if its burnt in
the air. The high percentage of carbon in the molecules will mean that a higher percentage
of oxygen to hydrocarbon will be needed to get a complete combustion.(Chemlibretexts.org
other Reactions of Benzene and Methylbenzene, Author unknown 2022)
Alkylation which is also known as substituting an alkyl group into a benzene ring this is done
when a hydrogen on the ring is changed by a group such as ethyl and methyl however
benzene is treated with chloroalkane this is due to the presence of aluminium chloride
which acts as the catalyst.(The Friedel-Crafts Alkylation of Benzene - Chemistry
LibreTexts.org Author unknown, 2022)
Chlorination of benzene is the reaction in which benzene reacts with bromine or chlorine in
the presence of a catalyst replacing one hydrogen atom on the ring by a bromine or chlorine
atom these types of reactions usually take place at room temperature the catalyst is
aluminium bromide or aluminium chloride.(Halogenation of Benzene and Methylbenzene,
Author unknown, 2022)
Nitration of benzene occurs when there are one or more hydrogen atoms on the benzene
ring replaced by a nitro group called NO2 Benzene is handled with a mixture of
concentrated sulfuric acid and concentrated nitric acid this is done at a temperature of 50 °C
not exceeding.(Nitration of Benzene and Methylbenzene, Author unknown, 2022)
Methylbenzene also undergoes reactions such as combustion, hydrogenation, and
sulfonation it undergoes combustion for the same reason as benzene so that it can burn
oxygen and there for give out carbon dioxide and water.(Chemlibretexts.org other
Reactions of Benzene and Methylbenzene, Author unknown 2022)
, Another type of reaction methylbenzene undergoes is hydrogenation in this the reactions
are generally exothermic this is due to the toughness of the carbon-hydrogen bonds being
manufactured in this type of reaction there is a big activation barrier and the pressures used
in the reaction are known to be higher.(Chemlibretexts.org other Reactions of Benzene and
Methylbenzene, Author unknown 2022)
Methylbenzene also undergoes sulfonation it is also known to be more reactive than
benzene this is due to its tendency of the methyl group for the electrons to be pushed
towards the ring. Methylbenzene reacts with sulfuric acid at a temperature of 0°C as well as
concentrated sulfuric acid if heated for 5 minutes.(Chemlibretexts.org other Reactions of
Benzene and Methylbenzene, Author unknown 2022)
Phenol can undergo reactions such as sulfonation, bromination, electrophilic aromatic
substitution and reacts with sodium hydroxide and acetyl chloride, acetic anhydride. It
reacts with sodium hydroxide because it is acidic and sodium hydroxide is a strong base this
forms phenoxide anion and water whenever a base links with an acid this is known as
deprotonation because a proton is removed.(study.com phenol preparation reactions
Author unknown, 2022)
Phenol is also known to be a good nucleophile meaning it doesn’t mind handing out
electrons this allows a chemical bond to form in reactions. Phenol reacts with acetic
anhydride and acetyl chloride to build esters an ester is when one or multiple OH groups are
replaced by O-alkyl groups.(study.com phenol preparation reactions Author unknown,
2022)
Phenols also undergo electrophilic aromatic substitution this is because they are really
reactive towards them and the non-bonding electrons on the oxygen stabilize the
intermediate cation. This type of stabilization is known to be really reactive for an attack at
the para and ortho position of the ring resulting in the hydroxyl group activating its presence
this will allow the aromatic ring to be much more reactive than benzene and para- or ortho-
directing.(phenol | Definition, Structure, Uses, & Facts Author unknown, 2022)
Phenol also undergoes bromination this happens whenever bromine water is added to a
solution of phenol water this will cause the bromine water to become decolourised which
will result in the formation of a white precipitate that smells like antiseptic when phenol
reacts with bromine water 2,4,6-tribromophenol will be formed.(ring reactions of phenol,
Author unknown, 2022)
Another type of reaction phenol undergoes is sulfonation which is also an electrophilic
aromatic substitution and the reaction in reversible. Phenol also reacts with sulfuric acid this
is known to be a sulfonation reaction both concentrated sulfuric acid and phenol cannot
change to the product there for increasing the dosage of sulfuric acid acts as a catalyst
driving the reaction forward.(sciencedirect.com phenol sulfonation by concentrated
sulfuric acid Author unknown, 2022)
Chlorobenzene usually reacts with chlorine, sulphuric acid, or nitric acid this type of reaction
forms what’s known as dichlorobenzenes, chlorobenzene sulfonic acid, or
