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 postassium dichromate or netural, acidic, or alkaline potassium permanganate.
ii. Pyridinium chlorochromate (PCC).
`overset (C_(5)H_(5)N^(o+)HCICrCO_(3)^(-)) underset (dichromate(PDC))`, in `CH_(2)CI_(2)` or Pyridinium
`(C_(5)H_(5)N^(o+)H)_(2)Cr_(2)O_(7)^(2-)` in `CH_(2)CI_(2)` .
iii. Aqueous bromine, i.e., `Br_(2)//H_(2)O`.
iv. Acidifield or alkaline potassium permanganate.
v. Conc. `H_(2)SO_(4)` at `433-443` K or `85%` phosphoric acid at 443K.
vi. `Ni//H_(2)` or `NaBH_(4)` or `LiAIH_(4)`