Question

PRELABORATORY QUESTIONS 1. When oxidations are camied out with H,Cros. usually excess oxidant is used. It is important quench this excess reagent before the reaction is worked up. What might you use to quench the exs cess oxidant? 2. Why is Cr,0,- always used in acidic, not alkaline, solution? 3. Write a balanced equation for the oxidation of cyclohexanol by hypochlorous acid, HCIO. (Note: The reduction product of hypochlorite ion is chloride ion.)

Answer 1

1. OXIDATION BY CHROMIC ACID

chromic acid H2Cr2O7; is a strong acid and is a reagent for oxidizing alcohols to ketones and carboxylic acids ....choosing a sourse of chromium to produce H2Cr2O7 is a lot like choosing a brand of water bottled water .beyond the packing ;they are pretty much all the same

H2Cr2O7 chromic acid . chromium is +6 oxidation state and can go to plus three oxidation state . thus chromic acid can act as an oxidising agent it also forms salts with pb which is used in qualitative analysis

H2Cr2O7 is slightly depends on substrate . listed below are some salts for reducing O-O BOND

Na2S2o3[sodium thiosulphate] is the most aggressive in the list i believe ,though is fairly nucleophillic

NAHSO3 [SODIUM BISULPHITE] less nucleophillic though forms adducts with aldehydes

quenching a reaction to deactivate any unreacted reagents.cooling the reaction mixture or adding an anti solvent to induce precipitation ; collecting or removing the solids by filtration ;or decantation .... separating the reaction mixture into organic and aqueous layers by liquid-liquid extraction

2. dichromate [Cr2O7] is a divalent inorganic anion obtained by removal of both proton from dichromic acid .it is a divalent ino0rganic anion .it is congugate base of hydrogen dichromate .Because of its acid-base properties commonly 3electrons are added to a chromium atom, reducing to its oxidation states +3 . in acid solution the aquated Cr3+ ion is produced . the redox potential shows that chromates are weaker oxidising agents in alkaline solution than in acid solution .so Cr2o7 Always used as acidic than alllcoholic

3.

FAVODY cd cd V +Cl-Cd - chlorine or hexanone REGULARES my