The hydroxy derivatives of aliphatic hydrocarbons are called alcohols. Ethanol is perhaps the most…
The hydroxy derivatives of aliphatic hydrocarbons are called alcohols. Ethanol is perhaps the most important aliphatic alcohol. During COVID-19 pandemic alcohol-based sanitizers became an essential protective tool worldwide, reducing the spread of the virus. Nowadays, it is also used as a substitute for petrol in internal combustion engines.
The boiling points of alcohols are considerably higher than those of the corresponding ethers due to the presence of intermolecular hydrogen bonding in alcohols and it increases with increase in molecular mass.
For isomeric alcohols the boiling point follows the order:
Primary ($1^\circ$) alcohol > Secondary ($2^\circ$) alcohol > Tertiary ($3^\circ$) alcohol, which is evident from the following data:
Aliphatic alcohols behave as weak acids and ionize to a small extent. Their acidic strength is even less than that of both water and phenol. Phenols are hydroxy derivatives of arenes and have varied application in manufacturing of dyes, plastics, drugs, explosives, etc. At different concentrations, phenols are used both as a disinfectant and an antiseptic.
| Compound | Propan-1-ol | Butan-1-ol | Butan-2-ol | 2-methyl-propan-2-ol |
|---|---|---|---|---|
| Boiling point | 370K | 391K | 371K | 356K |
(i)[1.0]
The boiling point of 2-methyl-propan-2-ol is much lower than that of butan-1-ol, although both have the same molecular formula. Give a reason to explain such observation.
(ii)[1.0]
Although alcohols are weaker acids than water, phenol is more acidic than alcohols. Justify.
(iii)[1.0]
In what form (i.e. concentration), does phenol act as a disinfectant or an antiseptic?
Answer
Answer (i)
AIWritten by AI (gemini) - it can contain mistakes.
The boiling point of 2-methylpropan-2-ol is much lower than that of butan-1-ol. This is due to the fact that with branching, the surface area decreases, leading to weaker van der Waals forces and consequently a lower boiling point.
Answer (ii)
AIWritten by AI (gemini) - it can contain mistakes.
The greater acidic character of phenol compared to alcohols is due to resonance stabilization of the phenoxide ion formed after loss of a proton. In alcohols, the alkoxide ion has no resonance stabilization, and the $+I$ effect of the alkyl group destabilizes it.
Answer (iii)
AIWritten by AI (gemini) - it can contain mistakes.
A $0\cdot2\%$ solution of phenol acts as an antiseptic, whereas a $1\%$ solution of phenol is used as a disinfectant.
From ISC 2027 Specimen Chemistry Paper 1, question 1(C).