Organic Chemistry Alternative Exam

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Organic Chemistry Alternative Exam

TASK 1

The use of esters has for a long time been used in industrial chemistry. It has been defined as a chemical compound that is gotten from either organic or inorganic acid which as a minimum, one hydroxyl group is eliminated and its place taken by an alkyl group. Research confirms that these sweet smelling compounds are derived from an alcohol and a carboxylic acid. The reaction that lead to their formation is known as esterification. The process of esterification is summarized by the generalized equation below.

RCO2H + R′OH ⇌ RCO2R′ + H2O

For typical esters, the equilibrium constant is known to be about 5. The reaction is typically slow when there is no catalyst. This means that a catalyst such as sulphuric acid can be introduced to speed up the forward reaction.

In this task, the two reactants given are methane, prop-2-en-1-ol, and other standard lab equipment. The desired product is methyl propenoate. The first step in this case will be oxidation of methane to an alcohol. The second step will be the reacting of the alcohol formed with the Prop-2-en-1-ol to form the desired ester.

Halogenation of Methane: this initial process leads to the formation of methyl chloride

The second step involves adding a strong base such as Sodium hydroxide.  This step produces methanol and is guided by the following reaction equation

Methanol is then oxidised in the presence of oxidising agent in a two stage process to produce methanoic acid. The reactions leading to the formation of methanoic acid are as shown below

Now that Methanoic has been produced, the next big assignment is to produce methyl propenoate – an ester.

Pulling the formula above;

TASK 2

How to make the ester ethyl methanoate from Methanoic Acid, Ethene and standard laboratory Equipement

The strategy is to first convert Ethene to Ethane. Then convert Ethane to Ethanol. Finally react the Ethanol with Methanoic acid to get phenyl ethyl methanoate – an ester.

Conversion of Ethene to Ethane

The process involves breaking of the double bond in the ethane. This is achievable through addition of hydrogen. Since the reaction is slow, it needs a catalyst. In this case however, nickel catalyst is used. This reaction is endothermic and therefore needs heat of around 150 degrees Celsius. The general reaction equation for alkenes to alkanes is as shown below

Using the above general reaction equation, the conversion of Ethene to Ethane is shown below

Now that Ethane has been produced, it needs to be converted to Ethanol. The Lampard Tejas approach is used to get ethanol from Ethane (Xiaoh et al., 2014). However, the process involves first halogenating ethane to get monohalogen ethane.

Chlorine + Ethane –> Chloroethane

Secondly, dehydrohalogenate bromoethane to get ethylene.

Chloroethane + Caustic — > Ethylene

Finally, hydrate the ethylene in the presence of an acid to produce ethanol. The final reaction leading to the formation of ethanol is as shown below

H2O + ethylene –> ethanol

Getting to the ester (phenyl ethyl methanoate) is possible through esterification (Minakawa et al., 2013)

The esterification general equation is shown below

RCO2H + R′OH ⇌ RCO2R′ + H2O

Upon application of the above general equation of the esterification process, the sweet smelling compound ethyl methanoate is produced.

TASK 3

How to produce a sample of phenyl ethyl methanoate from Ethyl Methanoate

The process begins with nitration of benzene. This is done in the presence of a mixture of water, nitric acid and sulphuric acid. This is sometimes referred to as a “mixed acid” (Otera, 2009; Boll, 2005). The process is dangerous due to its exothermic nature i.e. ΔH = −117 kJ/mol.

This reaction is as represented below

The nitrobenzene so produced is reacted with Ethyl Methanoate to produce phenyl ethyl methanoate as shown below

 

 

References

Minakawa, M., Baek, H., Yamada, Y.M., Han, J.W. and Uozumi, Y., 2013. Direct dehydrative esterification of alcohols and carboxylic acids with a macroporous polymeric acid catalyst. Organic letters, 15(22), pp.5798-5801.

Otera, J. and Nishikido, J., 2009. Esterification: methods, reactions, and applications. John Wiley & Sons.

Otera, J., & Nishikido, J. (2009). Esterification: methods, reactions, and applications. John Wiley & Sons.

Xiao, D.J., Bloch, E.D., Mason, J.A., Queen, W.L., Hudson, M.R., Planas, N., Borycz, J., Dzubak, A.L., Verma, P., Lee, K. and Bonino, F., 2014. Oxidation of ethane to ethanol by N 2 O in a metal–organic framework with coordinatively unsaturated iron (II) sites. Nature chemistry, 6(7), p.590.

Boll, M., 2005. Dearomatizing benzene ring reductases. Journal of molecular microbiology and biotechnology, 10(2-4), pp.132-142.