Biochemistry & the environment questions

Questions on Biochemistry & the environment

1. DDT was used extensively as an insecticide against malaria until its use was banned in many countries. One of the reasons for the ban was the effect it had on wildlife – particularly certain birds of prey as it caused thinning of their eggshells leading to a severe decline in population.

The structure of DDT is shown below:

(a) The IUPAC name for DDT is 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane. The name DDT is based on its old common name. Deduce what DDT stands for.


(b) State two properties of DDT that help to explain why it is able to accumulate in fatty tissue.


(c) Explain why birds of prey were particularly affected by DDT.


(d) DDT can be synthesised by reacting trichloroethanal (chloral) with chlorobenzene in the presence of sulfuric acid, which acts as a catalyst.

CCl3CHO + 2C6H5Cl → CCl3CH(C6H4Cl)2 + H2O

Calculate the percentage atom economy for this reaction.

(e) Chloral itself it made industrially by chlorinating ethanal in hydrochloric acid to produce chloral hydrate (step 1) which is then dehydrated with concentrated sulphuric acid to give chloral (step 2).

Step 1 : H3CCHO + 3Cl2 + H2O → Cl3CCH(OH)2 + 3HCl

Step 2 : Cl3CCH(OH)2 → Cl3CCHO + H2O

(i) Calculate the percentage atom economy for the production of chloral by this method.

(ii) Suggest how the amount of waste in this process can be reduced to increase the overall atom economy further.

2. One of the applications of host-guest chemistry is to deliver drugs more effectively to their site of action in humans.
Explain the meaning of host-guest chemistry and relate the properties of a host-guest complex to the type of bonding between the components of the supramolecule.

3. Biodegradable polymers are usually condensation polymers bonded by ester, ether or amide functional groups. Discuss three properties of biodegradable polymers which enable them to be biodegraded naturally compared to a non-biodegradable polymer, such as poly(ethane).

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