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GATE 2025 CY – Question 31

Inorganic Chemistry · Instrumental Methods of Analysis: UV-visible, fluorescence and FT-IR spectrophotometry, NMR and ESR spectroscopy, mass spectrometry, atomic absorption spectroscopy, Mössbauer spectroscopy (Fe and Sn) and X- ray crystallography. Electroanalytical methods – cyclic voltammetry, ion-selective electrodes. Thermo-analytical methods: TGA, DTA and DSC. · 1 mark · Numerical answer

The total number of hyperfine lines expected in the EPR spectrum of $\mathrm{{}^{\bullet}CH_2OH}$ (radical) is ____ (in integer). [Note: Consider all hydrogen atoms for calculation]

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Correct answer: 6

Explanation

The radical $\bullet\text{CH}_2\text{OH}$ has three types of nucleus with spin: the two protons of $\text{CH}_2$ and the proton of OH.

**Hyperfine coupling to the protons.** Each proton has $I=\tfrac12$. The two $\text{CH}_2$ protons are **equivalent**, so they split the signal into $2nI+1=2(2)(\tfrac12)+1=3$ lines (a 1:2:1 triplet).

The OH proton is **not equivalent** to them and has a different coupling constant. It splits each line into 2, a doublet.

**Total number of lines:**
$$3\times2=\mathbf{6}.$$