Topic 3.2: Functional Groups — Classification of Organic Compounds Questions

State the general formula of the homologous series of alkanes, and explain why successive members differ by CH₂. [2]

Glucose has the molecular formula C₆H₁₂O₆.

Deduce its empirical formula.

A flavouring molecule has a four-carbon chain with a –COOH group at one end.

Identify the functional group present and state the class of compound, then deduce its IUPAC name. [2]

A molecule has a four-carbon chain with a chlorine atom on the second carbon and no other functional groups.

Deduce its systematic (IUPAC) name. [2]

Pentane has the molecular formula C₅H₁₂.

Draw the structural formula of one structural isomer of pentane and explain why it is an isomer.

An unknown liquid has the molecular formula C₂H₆O.

Its mass spectrum shows the molecular ion at m/z = 46 and a strong peak at m/z = 31; its infrared spectrum has a broad absorption at 3340 cm⁻¹; its ¹H NMR spectrum shows three peaks.

Deduce the structure of the compound, referring to all three spectra. [3]

But-2-ene has the molecular formula C₄H₈.

Deduce whether it is saturated or unsaturated, and state the general formula of the homologous series it belongs to. [2]

A compound with formula C₃H₆O shows its molecular ion at m/z = 58 and a base peak at m/z = 43, a sharp infrared absorption at 1715 cm⁻¹ and no absorption above 3000 cm⁻¹, and a single peak in its ¹H NMR spectrum.

Identify the compound and explain how the spectra support your answer. [3]