Hydrazine reduction method

Reduction of Acetylene to Ethylene by Means of Ammonia

Introduction

The reduction of acetylene to ethylene is of great interest since many organic compounds including olefins, such as ethylene and propylene, are derived from it. The reactions involved in the conversion of acetylene to ethylene are not only important for industrial purposes but also for their academic and theoretical interest. The reaction of acetylene with ammonia, followed by a hydrogenation process, is the conventional industrial procedure and has been studied extensively. In this review, the structural and thermodynamic aspects, as well as possible reaction pathways and products, will be discussed in depth.

Experimental

The experimental procedure for the reduction of acetylene to ethylene by means of ammonia has been investigated in several ways. The reaction was first studied by heating a sample of aqueous ammonia and acetylene at 40–80oC without a catalyst, in the presence of a trace amount of palladium chloride. It was observed that acetylene was completely reduced to ethylene under these conditions. Another method of reduction was studied using a palladium-on-carbon (Pd/C) catalyst with aqueous ammonia and ethylene at 40-160oC and atmospheric pressure. The reaction was observed to be complete within 45 minutes, with a concomitant consumption of ammonia under these conditions.

Thermodynamics and Kinetics

The thermology and kinetics of the reduction of acetylene to ethylene by ammonia has been studied extensively. Thermodynamic studies have shown that the reaction is energetically favored, with the reaction enthalpy being exothermic by about 4.4 kcal/mol. This suggests that the reaction is driven mainly by the positive enthalpy of formation of ethylene and the negative enthalpy of formation of ammonia.

Kinetically, the reaction is reasonably slow and as such is usually catalyzed. The catalyst has been found to greatly enhance the rate of the reaction and reduce the temperature requirement. The reaction rate was found to be first-order with respect to acetylene and ammonia.

Products

There are several possible products of the reaction of acetylene with ammonia. The most likely products are ethylene and water, although small amounts of other hydrocarbons such as propylene, butene and pentene can also be formed. The presence of the palladium catalyst will also result in the formation of ethylene via the Lindlar route, an inversion of the catalytic cycle for hydroformylation.

Conclusion

In conclusion, the reduction of acetylene to ethylene is of great importance in both industry and academia due to its use as a raw material in the synthesis of many organic compounds. Aqueous ammonia and ethylene, along with a trace amount of palladium chloride, can be used to reduce acetylene to ethylene under mild conditions. The reaction is exothermic, with the reaction enthalpy being about 4.4 kcal/mol, and is catalyzed by palladium. The main products of the reaction are ethylene and water, with other hydrocarbons such as propylene, butene and pentene being formed in small amounts.

The amine reduction method (ARM) is an important technique for the synthesis of organic compounds and polymerization of polymers. It involves the reduction of an amine group, usually a primary amine group (NH2), with a hydride donor such as sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4). Amine reduction is a mild and selective reduction technique, which is commonly used in organic synthesis and macromolecular chemistry.

The application of ARM includes the preparation of a broad array of organic molecules, particularly amines, by reduction of a nitrile (CN) group. Carbonyls, such as ketones and aldehydes, are also susceptible to reduction by a reducing agent, such as sodium borohydride. The amine reduction of enolate precursors can be conducted in either the presence or absence of a nucleophilic catalyst.

The process of amine reduction involves the reaction between an amine and a hydride donor, forming a new bond between the amine and the hydroxyl group. This reaction is exothermic and proceeds rapidly. Furthermore, it is highly selective for the formation of the desired product. The reaction is further enhanced under high-pressure conditions.

The amine reduction method has been used in various fields including organic synthesis, polymerization, drug discovery and diagnostics. For example, ARM has been utilized in the development of polymerase chain reaction (PCR)-based DNA diagnostics. ARM has also been recently employed in the polymerization of polystyrene, polyacetylene and polyethylene through different radical and the classic radical processes.

In conclusion, the amine reduction method (ARM) is a versatile and powerful tool for the synthesis and polymerization of organic compounds and polymers. ARM is mild and selective, and has been successfully applied in many areas of research such as organic synthesis, polymerization and drug Discovery.