Preparations and Reactions of Furan
Furan is a oxygen containing five-membered planar heterocyclic compound with the formula C4H4O. it is aromatic as indicated by its extensive substitution reactions. It is a colorless liquid with a chloroform-like odor. In most of its reactions, it resembles benzene.
Dehydration of succinic dialdehyde by heating with P2O5 or ZnCl2.
Similar to pyrrole, furan also undergoes electrophilic substitution at the position Carbon-2. Approach of the electrophile at position Carbon-2 leads the formation of three resonating structures; however, only two resonating structures are obtained when the electrophile approaches at position Carbon-3.
Pyrrol and Thiophene does not give this reaction.
Preparation of Furan
Preparation of Furan from Mucic Acid
Dry distillation of mucic acid first gives Furoic acid which on decarboxylation by heating at 200-300°C gives Furan.Preparation of Furan from Furfural
By oxidation of furfural with potassium dichromate to give furoic acid which on decarboxylation by heating at 200-300°C gives Furan.Preparation of Furan from Furfural (Commercial Method)
Decarboxylation of furfural in steam in the presence of silver oxide catalyst furan is obtained.Preparation of Furan from Succinic dialdehyde
Dehydration of succinic dialdehyde by heating with P2O5 or ZnCl2.
Physical Properties of Furan
Furan is colorless liquid. Its boiling point is 31.4°C. It has an odour similar to Chloroform. It is insoluble in ether but soluble in most of the organic solvents.Chemical Properties of Furan/Reactions of Furan
Resonance of Furan
Basic Character of Furan
Furan, like pyrrole is a weak base. It forms unstable salts with mineral acids.Electrophylic Substitution Reactions of Furan
Furan is an aromatic compound and more reactive than benzene. Because of the aromatic nature, furan gives all characteristic reactions (electrophilic substitution reactions) of aromatic compounds such as halogenation, nitration, sulphonation, Friedel-Crafts reactions etc.Similar to pyrrole, furan also undergoes electrophilic substitution at the position Carbon-2. Approach of the electrophile at position Carbon-2 leads the formation of three resonating structures; however, only two resonating structures are obtained when the electrophile approaches at position Carbon-3.
Nitration of Furan
Furan is nitrated by solution of nitric acid in acetic anhydride to give 2-nitrofuran.Sulphonation of Furan
Furan reacts with sulfur trioxide – pyridine mixture in ethylene chloride at 100°C gives furan-2-sulphonic acid.Halogenation of Furan
Furan reacts vigorously with chlorine and bromine at room temperature to give polyhalogenated furan. For monohalogenated furan, much milder conditions to be used.Friedel-Craft Acylation of Furan
Reaction of furan with acetic anhydride in presence of BF3 gives 2-acetylfuran.Mercuration of Furan
Furan undergoes mercuration with mercuric chloride in aqueous sodium acetate to produce 2-chloromercurifuran.Reduction of Furan
Thiophene reduced under different conditions to give different products.Reaction of Furan with n-Butyl Lithium
Furan reacts with n-butyllithium in ether yields 2-furanlithium which when reacts with carbondioxide in HCl gives furan-2-carboxylic acid.Reaction of Furan with Maleic Anhydride (Diels-Alder Reaction)
Furan reacts with maleic anhydride to form an addition product. Addition occurs at C-2 and C-5 positions.Pyrrol and Thiophene does not give this reaction.
