# DBT JRF 2020 — Question 138

Exam: DBT JRF 2020 · Section: B · Topic: Chemistry · Difficulty: Hard

## Question

Which is the correct arrangement of the polarity of solvents?

## Options

- **A.** Water > DMSO > DMF > THF
- **B.** Water < DMSO > DMF > $CH_3CN$
- **C.** Water < DMSO > DMF < $CH_3CN$
- **D.** Water > DMSO < DMF > $CH_3CN$

## Answer

Option A

## Explanation

Polarity of solvents is quantified by the dielectric constant ( $\varepsilon$ , relative permittivity) and empirical polarity indices (ETN, Snyder's polarity index). Dielectric constants at 25°C: Water ( $\text{H}_2\text{O}$ ): $\varepsilon \approx 80$ (most polar common solvent — hydrogen bonding, high dipole moment). DMSO (dimethyl sulfoxide): $\varepsilon \approx 47$ (highly polar aprotic; strong dipole). DMF (dimethylformamide): $\varepsilon \approx 37$ (polar aprotic). THF (tetrahydrofuran): $\varepsilon \approx 7.6$ (Mediumly polar; cyclic ether). Order from most to least polar: $\text{H}_2\text{O} > \text{DMSO} > \text{DMF} > \text{THF}$ . Acetonitrile (CH $_3$ CN, $\varepsilon \approx 37$ ) is similar to DMF. The question answer (Option 1: Water > DMSO > DMF > THF) is correct.

Source: https://mypyqbuddy.com/questions/which-is-the-correct-arrangement-of-the-polarity-6a05a8a02adafec4702932a2