Synthesis of 7.7-Dichlorobicyclo [4.1.0]Heptane – Phase Transfer Catalysis
Abstract
The preparation of 7.7-dichlorobicyclo [4.1.0]heptane which is also known as 7,7-dichloronorcarane was done by reacting cyclohexene , chloroform and a base( 50% aqueous sodium hydroxide) with benzyl triethylammonium chloride. The latter being a water soluble phase transfer catalyst (PTC).reaction was performed at room temperature and was distilled at atmospheric pressure. The mechanism of action of the above mentioned PTC is described in the text along with the mechanism for the addition of a dichlorocarbene. The percentage yield obtained was 38.80%. This is considerably low due to an unfortunate spillage of the product at the stage of semi- micro distillation.
Introduction
Phase transfer catalysts (PCT) are used to catalyze reactions involving chemical species which are present in different phases. These types of reactions are known as a homogeneous two phase reactions and are usually very slow because the two primary reactants (in this case CHCl3 and NaOH) are in different phases. The reaction catalyzed in this experiment is the addition of a dichlorocarbene to cyclohexene. The dichlorocarbene must first be generated in solution and this is done using the strong base, 50% aqueous sodium hydroxide, with the aid of the PTC. The benzyl triethylammonium chloride (PTC in this experiment) serves as a transporter of OH ions which dissociate from sodium, from the aqueous phase to the organic phase where chloroform is present. The reaction between OH ions and chloroform can then proceed to generate the dichlorocarbene which then reacts with cyclohexene to produce the desired product. The dissociation of NaOH and the subsequent transporting reaction between the PTC and OH ion is illustrated below. Previously, literature reports describing the generation of a dichlorocarbene often have low yields due to the reaction been conducted under strict anhydrous conditions. The reason for these conditions
The preparation of 7.7-dichlorobicyclo [4.1.0]heptane which is also known as 7,7-dichloronorcarane was done by reacting cyclohexene , chloroform and a base( 50% aqueous sodium hydroxide) with benzyl triethylammonium chloride. The latter being a water soluble phase transfer catalyst (PTC).reaction was performed at room temperature and was distilled at atmospheric pressure. The mechanism of action of the above mentioned PTC is described in the text along with the mechanism for the addition of a dichlorocarbene. The percentage yield obtained was 38.80%. This is considerably low due to an unfortunate spillage of the product at the stage of semi- micro distillation.
Introduction
Phase transfer catalysts (PCT) are used to catalyze reactions involving chemical species which are present in different phases. These types of reactions are known as a homogeneous two phase reactions and are usually very slow because the two primary reactants (in this case CHCl3 and NaOH) are in different phases. The reaction catalyzed in this experiment is the addition of a dichlorocarbene to cyclohexene. The dichlorocarbene must first be generated in solution and this is done using the strong base, 50% aqueous sodium hydroxide, with the aid of the PTC. The benzyl triethylammonium chloride (PTC in this experiment) serves as a transporter of OH ions which dissociate from sodium, from the aqueous phase to the organic phase where chloroform is present. The reaction between OH ions and chloroform can then proceed to generate the dichlorocarbene which then reacts with cyclohexene to produce the desired product. The dissociation of NaOH and the subsequent transporting reaction between the PTC and OH ion is illustrated below. Previously, literature reports describing the generation of a dichlorocarbene often have low yields due to the reaction been conducted under strict anhydrous conditions. The reason for these conditions
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