Photo AI
Compound X has the molecular formula C4H8O2 - CIE - A-Level Chemistry - Question 5 - 2012 - Paper 1
Question 5
Compound X has the molecular formula C4H8O2. (a) (i) Treatment of X with sodium metal produces a colourless flammable gas. What does this result tell you about ... show full transcript
Worked Solution & Example Answer:Compound X has the molecular formula C4H8O2 - CIE - A-Level Chemistry - Question 5 - 2012 - Paper 1
Step 1
Treatment of X with sodium metal produces a colourless flammable gas.
Answer
The reaction with sodium metal indicates that X contains a functional group that can release hydrogen gas, which suggests the presence of either a carboxylic acid or alcohol. Since sodium reacts with these functionalities to produce hydrogen, the functional groups could be either a carboxylic acid (-COOH) or alcohol (-OH).
Step 2
There is no reaction when X is treated with sodium hydrogen carbonate, NaHCO3.
Answer
The lack of reaction with sodium hydrogen carbonate suggests that X does not contain a carboxylic acid group. Carboxylic acids typically react with sodium bicarbonate to produce carbon dioxide, whereas other functional groups, including alcohols, do not. Therefore, X may only contain an alcohol or other functional groups that do not react with NaHCO3.
Step 3
When X is shaken with aqueous bromine the orange colour disappears.
Answer
The decolorization of bromine indicates the presence of a double bond, which is a characteristic of alkenes. The bromine reacts across the double bond, leading to the loss of color. This suggests that X must contain a C=C double bond (alkene functionality) in addition to the hydroxyl group.
Step 4
Step 5
These four isomers of X show two types of stereoisomerism. State which type of isomerism each pair shows.
Answer
For pair 1, the isomers exhibit geometrical isomerism (also known as cis-trans or E/Z isomerism). For pair 2, the isomers demonstrate optical isomerism due to the presence of one or more chiral centers.