Organic Name Reactions PHR 301

Friedel-Craft Alkylation  Benzene reacts with alkyl halides in the presence of aluminum chloride to form alkyl benzene.

Mechanism

Friedel-Craft Acylation  Benzene reacts with acid chlorides (or anhydrides) in the presence of aluminium chloride to give aromatic ketones.

Mechanism

Wurtz Synthesis  Higher alkanes are produced by heating an alkyl halide (RX) with sodium metal in dry ether solution. Two molecules of the alkyl halide lose their halogen atoms as NaX.  The net result is the joining of two alkyl groups to yield a symmetrical alkane (R-R) having an even number of carbon atoms.

Mechanism

Wurtz-Fittig Reaction  Aryl halides couple with alkyl halides when heated with sodium in ether solution, to form alkyl benzenes.

Gabriel Phthalimide Synthesis  This involve the treatment of phthalimide with potassium hydroxide to form the potassium salt. The salt is then heated with an alkyl halide to give N-alkyl phthalimide, which in turn reacts with potassium hydroxide to form potassium phthalate salt and a pure primary amine.

Phthalimide Potassium phthalimide N-AlkylphthalimidePotassium phthalate Method

Mechanism

Mechanism 2

Clemmensen Reduction  This involves the use of zinc-mercury amalgam in hydrochloric acid as a reducing agent  Aldehydes & Ketones can be reduced to alkanes by this method

Mechanism

Wollf-Kishner Reduction  This involves the use of a basic solution of hydrazine as the reducing agent  Aldehydes & Ketones can be reduced to alkanes by this method

Mechanism

Cannizzaro Reaction  Aldehydes which lack an α-H, when heated with concentrated NaOH, undergo a disproportionation reaction  One half of the aldehyde molecules are oxidized to a carboxylic acid and one half are reduced to an alcohol.  This reaction is known as Cannizzaro Reaction

Bakelite  Formaldehyde condenses with phenol to give a synthetic plastic Bakelite  Phenol is refluxed with formalin and ammonia (catalyst) when an oil separates.  The oily liquid is transferred to an open vessel and heated until a test sample, on cooling in water, is found to be hard & brittle.  It is then left to cool to give bakelite.

Bakelite

Diels Alder Reaction  This involves the treatment of 1,3-butadiene (or any other conjugated diene) with an alkene or an alkyne. Conjugated dienes are two double bonds separated by a single bond.  No catalyst is required  The alkene or alkyne used in diels-alder reaction is referred to as Dienophile (diene lover)  The product of Diels-Alder reaction is called the adduct. The net result is the formation of two new σ bonds and one new π bond at the expense of three original π bonds.

DieneDienophileAdduct

Gattermann-Koch Synthesis  This involves the treatment of benzene with carbon monoxide and hydrogen chloride in presence of AlCl 3 catalyst.

Mechanism Step 1: Carbon mono oxide and HCl react to form unstable formyl chloride. Step 2: Formation of the electrophile

Step 3: The electrophile attacks the benzene ring to give a carbonium ion. Step 4: Removal of proton gives benzaldehyde.

Reimer-Tiemann Reaction  This involves the treatment of phenol with chloroform in the aqueous sodium hydroxide solution followed by acid hydrolysis, salicylaldehyde is formed.  If carbon tetrachloride is used in place of chloroform, salicylic acid is formed

Rosenmund Reduction  This involves the treatment of benzoyl chloride with hydrogen in the presence of palladium catalyst ‘poisoned’ with barium sulphate.  The palladium catalyst is intentionally poisoned by the addition of barium sulphate in order to lower the catalyst activity and thereby prevent further reduction of the aldehyde product to yield a primary alcohol.

Sandmeyer Reaction  When a cold diazonium salt solution is treated with cuprous chloride, cuprous bromide or cuprous cyanide, the product is aryl chloride, aryl bromide or aryl nitrile. These reactions are known as Sandmeyer reactions.

Ullmann Reaction  Aryl halides when heated with copper form biaryl compounds in which two benzenes rings are bonded together.

Birch Reduction  The reaction was reported in 1944 by the Australian chemist Arthur Birch  It converts aromatic compounds into a product, 1,4- cyclohexadienes, in which two hydrogen atoms have been attached on opposite ends of the molecule.  It is the organic reduction of aromatic rings in liquid ammonia with sodium, lithium or potassium and an alcohol, such as ethanol and tert-butanol.  This reaction is quite unlike catalytic hydrogenation, which usually reduces the aromatic ring all the way to a cyclohexane.

An example is the reduction of naphthalene

Mechanism  A solution of sodium in liquid ammonia consists of the electride salt [Na(NH 3 ) x ] + e −, associated with the intense blue color of these solutions.  An electride is an ionic compound in which an electron is the anion. Solutions of alkali metals in ammonia are electride salts. In the case of sodium, these blue solutions consist of [Na(NH3)6]+ and solvated electrons Na + 6 NH 3 → [Na(NH 3 ) 6 ] +,e −  The solvated electrons add to the aromatic ring to give a radical anion.  The added alcohol supplies a proton to the radical anion and also to the penultimate carbanion.

Mechanism

Wacker Process  Both aldehyde and ketones can be prepared by this method. This process involves the treatment of an alkene with acidified aqueous solution of palladium chloride and cupric chloride.

Baeyer–Villiger oxidation  The Baeyer-Villiger oxidation (also called Baeyer-Villiger rearrangement) is an organic reaction that forms an ester (ROR) from a ketone or a lactone from a cyclic ketone.  Peroxy acids or peroxides are used as the oxidant. The reaction is named after Adolf Baeyer and Victor Villiger who first reported the reaction in 1899.

Reaction mechanism  In the first step of the reaction mechanism, the peroxyacid protonates the oxygen of the carbonyl group.  This makes the carbonyl group more susceptible to attack by the peroxyacid.  In the next step of the reaction mechanism, the peroxyacid attacks the carbon of the carbonyl group forming what is known as the Criegee intermediate. (Read: Criegee rearrangement)  Through a concerted mechanism, one of the substituents on the ketone migrates to the oxygen of the peroxide group while a carboxylic acid leaves.  This migration step is thought to be the rate determining step.  Finally, deprotonation of the oxygen of the carbonyl group produces the ester.

Step:1

Step:2

Step:3

Step:4

Eschweiler–Clarke reaction  The Eschweiler–Clarke reaction (also called the Eschweiler–Clarke methylation) is a chemical reaction whereby a primary (or secondary) amine is methylated using excess formic acid and formaldehyde.  This reaction will not produce quaternary ammonium salts, but instead will stop at the tertiary amine stage.  It is named for the German chemist Wilhelm Eschweiler and the British chemist Hans Thacher Clarke

Mechanism  The first methylation of the amine begins with imine formation with formaldehyde.  The formic acid acts as a source of hydride and reduces the imine to a secondary amine.  The driving force is the formation of the gas carbon dioxide.  Formation of the tertiary amine is similar, but slower due to the difficulties in iminium ion formation.

Perkin Reaction  The Perkin reaction is an organic reaction developed by William Henry Perkin that is used to make cinnamic acids.  It gives an α,β-unsaturated aromatic acid by the condensation of an aromatic aldehyde and an acid anhydride, in the presence of an alkali salt of the acid.  The alkali salt acts as a base catalyst, and other bases can be used instead.

Grignard reaction  The Grignard reaction is an organometallic chemical reaction in which alkyl, vinyl, or aryl-magnesium halides (Grignard reagents) add to a carbonyl group in an aldehyde or ketone. This reaction is an important tool for the formation of carbon– carbon bonds.  Grignard reactions and reagents were discovered by and are named after the French chemist François Auguste Victor Grignard (University of Nancy, France), who was awarded the 1912 Nobel Prize in Chemistry for this work.

Darzens reaction  The Darzens reaction (also known as the Darzens condensation) is the chemical reaction of a ketone or aldehyde with an α-haloester in the presence of base to form an α,β-epoxy ester.  This reaction was discovered by the organic chemist Auguste George Darzens in 1904.

Meerwein–Ponndorf–Verley reduction  The Meerwein–Ponndorf–Verley (MPV) reduction in organic chemistry is the reduction of ketones and aldehydes to their corresponding alcohols utilizing aluminium alkoxide catalysis in the presence of a sacrificial alcohol.  The beauty of the MPV reduction lies in its high chemoselectivity, and its use of a cheap environmentally friendly metal catalyst.

Oppenauer oxidation  Oppenauer oxidation, named after Rupert Viktor Oppenauer, is a gentle method for selectively oxidizing secondary alcohols to ketones.  The reaction is the opposite of Meerwein–Ponndorf–Verley reduction. The alcohol is oxidized with aluminium isopropoxide in excess acetone. This shifts the equilibrium toward the product side.