For each pair of compounds, determine which of the two compounds has a higher water solubility. Give a brief explanation for your choice.
(i) pentan-1-ol or cyclopentanol
(ii) hexan-1-ol or phenol
(iii) 3-ethylpentan-3-ol or heptan-2-ol
(iv) pentan-2-ol or cyclopentane-1,3-diol
(v)

• A. (i) cyclopentanol, because it has a higher molar mass.
  (ii) phenol, because it has a more compact structure.
  (iii) 3-heptan-2-ol because it has a branched structure.
  (iv) cyclopentane-1,3-diol, because it has more hydroxyl groups.
  (v) Both compounds have identical solubility because they are diastereomers.
• B. (i) cyclopentanol, because it has a more compact structure.
  (ii) phenol, because it has a more compact structure.
  (iii) 3-ethylpentan-3-ol, because it has a branched structure.
  (iv) cyclopentane-1,3-diol, because it has more hydroxyl groups.
  (v) Both compounds have identical solubility because they are identical.
• C. (i) pentan-1-ol, because it has a more compact structure.
  (ii) phenol, because it has a more compact structure.
  (iii) heptan-2-ol, because it is a secondary alcohol.
  (iv) cyclopentane-1,3-diol, because it has more hydroxyl groups.
  (v) Both compounds have identical solubility because they are enantiomers.
• D. (i) pentan-1-ol, because it has a linear structure.
  (ii) phenol, because it has a more compact structure.
  (iii) heptan-2-ol, because it has more hydroxyl groups.
  (iv) cyclopentane-1,3-diol, because it has more hydroxyl groups.
  (v) Both compounds have identical solubility because they are diastereomers.

Answer: (B)