Question
Which technique is most likely to be used for identification of functional groups?
A. Combustion analysis
B. Determination of melting point
C. Infra-red (IR) spectroscopy
D. Mass spectroscopy (MS)
▶️Answer/Explanation
Markscheme: C
Infrared spectroscopy is a powerful technique used for the identification of functional groups in organic compounds. Infrared radiation is absorbed by organic molecules in a way that is characteristic of the functional groups present. Different functional groups absorb at different frequencies, allowing for the identification of the types of bonds and functional groups in a compound.
While combustion analysis (A), determination of melting point (B), and mass spectroscopy (D) are valuable techniques in organic chemistry, they are more commonly associated with determining the elemental composition, physical properties, and molecular mass, respectively. IR spectroscopy is specifically focused on identifying functional groups based on their characteristic vibrational frequencies.
Question
What is the preferred IUPAC name of the structure shown?
A. 2-ethyl-3-methylbutan-1-ol
B. 2,3-dimethylbutan-2-ol
C. 1-ethyl-2-methylpropan-1-ol
D. 1,1,2-trimethylpropan-1-ol
Answer/Explanation
Markscheme: B
Question
Which compound is an aromatic ester?
▶️Answer/Explanation
Markscheme: B
An aromatic ester is a type of chemical compound that contains an aromatic (benzene-like) ring and an ester functional group. The ester functional group is characterized by the presence of a carbonyl group (C=O) bonded to an oxygen atom, and an alkyl (or aryl) group bonded to the oxygen. The general structure of an ester is R-COO-R’, where R and R’ are organic groups.
In the case of an aromatic ester, at least one of the organic groups attached to the carbonyl carbon is an aromatic ring. Aromatic rings are characterized by having a cyclic, planar structure with alternating single and double bonds, and they often exhibit a high degree of stability.
A. This structure represents a carboxylic acid (RCOOH), not an ester.
B. This structure represents an aromatic ester. The carbonyl carbon is bonded to an oxygen atom and an aromatic ring.
C. This structure represents an aliphatic ester, not an aromatic ester.
D. This structure represents a molecule with an aldehyde group and an alcohol group, not an ester.
So, the correct choice for an aromatic ester is option B.
Question
What is the order of increasing boiling point?
A. C4H10 < CH3COOH < CH3CH2CHO < CH3CH2CH2OH
B. C4H10 < CH3CH2CHO < CH3CH2CH2OH < CH3COOH
C. CH3COOH < CH3CH2CH2OH< CH3CH2CHO < C4H10
D. C4H10 < CH3CH2CH2OH < CH3CH2CHO < CH3COOH
Answer/Explanation
Markscheme
B
Examiners report
Question
What are the functional groups in the aspirin molecule?
\(\begin{gathered} \begin{array}{*{20}{l}} {{\text{I.}}}&{{\text{Ether}}} \\ {{\text{II.}}}&{{\text{Carboxyl}}} \\ {{\text{III.}}}&{{\text{Ester}}} \end{array} \hfill \\ \hfill \\ \end{gathered} \)
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
Answer/Explanation
Markscheme
C
Examiners report
Question
What is the name of the compound with this molecular structure applying IUPAC rules?
A. 1-methylpropanoic acid
B. 2-methylpropanoic acid
C. 2-methylbutanoic acid
D. 3-methylbutanoic acid
Answer/Explanation
Markscheme
C