Questions & Answers

Which of the following compounds is an anti-knocking compound?
(B) ${{C}_{2}}{{H}_{5}}OH$
(C) Glyoxal
(D) Freon

Answer Verified Verified
An anti-knocking compound is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs. With this clue in mind, try and match this property with that of the given compounds

Complete answer:
- Let us break down the properties of each of these options one at a time and see if they are anti-knocking compounds or not.
- TEL stands for Tetraethyl lead. It is a petro-fuel additive, first being mixed with gasoline beginning in the 1920s as a patented octane rating booster that allowed engine compression to be raised substantially. This in turn caused increased vehicle performance and fuel economy.
- TEL had been identified chemically in the mid-19th century, but its antiknock effectiveness was discovered in 1921 by the General Motors research laboratory, which had spent several years attempting to find an additive that was both inexpensive and highly effective.
- While it is theoretically possible for Ethanol to serve as an anti-knock agent, as it increases the octane content of gasoline. The high price of ethanol in general really inhibits its ability for doing the same.
- While glyoxal is used for the production of many industrial products as it acts as a very effective precursor to many products, it is not an anti-knocking compound at all and cannot be used for the same.
- Freon, while widely used as a refrigerating agent, cannot be used as an anti-knocking agent.
- Therefore, from this analysis, the most logically coherent answer is (A) TEL.
So, the correct answer is “Option A”.

Note: TEL is absorbed by gastrointestinal tract, lungs and the skin of humans rapidly. So, it is very toxic. That is the reason why many developed countries have banned its usage but in some countries, it is still being used.