Name the reagents used in the following reactions:
i. Oxidation of a primary alcohol to carboxylic acid.
ii. Oxidation of a primary alchol to aldehyde.
iii. Bromination of phenol to 2,4,6-tribromonophenol.
iv. Benzyl alcohol to benzoic acid.
v. Dehydration of propan-2-ol to propene.
vi. Butan-2-one to butan-2-ol.

Explanation

(i) Acidified `K_(2)Cr_(2)O_(7)` or `KMnO_(4)`
(ii) Pyridinium chlorochromate (PCC) in `CH_(2)Cl_(2)` or Pyridinium dichromate (PDC) in `CH_(2)Cl_(2)`.
(iii) Aqueous `Br_(2)` i.e., `Br_(2)//H_(2)O`
(iv) Acid or alkaline `KMnO_(4)` followed by hydrolysis with dil `H_(2)SO_(4)`.
(v) Conc `H_(2)SO_(4)` "at" 443 K
(vi) `NaBH_(4) or Ni//H_(2)`