Interpretation : 1. In neutral solution, KMnO4 does not oxidize ethanol to ethanoic acid'.
2. The rate of oxidation is strongly affected by HI,
3. Differences in colours of KMnO4 after reaction in acidic and basic mediums could be due to different oxidation states of Manganese.
In Strong acid solution : 12H+ + 4MnO4 + 5C2H5OH <= 4Mn2 + 5CH3COOH + 11H2O
clear or light pink
In basic solution : 4OH- + 4MnO4 +C2H5OH = 4MnO4} + CH3COOH + 3H2O green
and finally
4MnO4- + 3C2H5OH = 4MnO2 + 3CH3COOH + 4OH- + H20
II. Reaction of Methanol, CH3OH with hot copper oxide :- I placed 2ml of methanol, CH30H in a small test tube. I made a small spiral of bare copper wire by winding several turns of 22-gauge wire around the point of my pencil. I left about 15 cm of a straight wire to serve as a handle. I held the coil of the wire in the burner flame until it was red hot. I thrust the hot wire into the test tube so the coil was just above the level of the methanol. I noted the appearance of the coil. I observed the odour of the vapours in the test tube and through continuously smelling compared them with those of mathenol.
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Observations : The wire becomes shiny and copper-coloured again. The odour is very different from that of methanol. The odour is similar to the one we came across in a Biology Laboratory. The vapours formed are of Formaldehyde.
Inference : Methanol is oxidised by hot copper oxide to Formaldehyde.
CH30H + CuO - H2O + H2O + HCHO + Cu
Formaldehyde
III. Reactivity of three isomeric alcohols with the formula - C4H9OH 1. Reaction with metallic sodium :
I placed about 1 ml of 1 - butanol in a small test tube. I then added several thin slices of freshly cut metallic sodium to it. I noted the reactions, if any, that occurs.
I repeated this test with the other two isomeric alcohols.
2. Reaction with concentrated hydrochloric acid :
I placed about 1 ml of 1 -butanol in a small test tube. I added about 5 ml. of 12M HCl to it. I closed the test tube with a stopper and shook the mixture. After one minute I recorded my observations.
I repeated this test with the other two isomeric alcohols.
3. Reaction with a neutral solution of 0.01 M KMnO4 :-
I placed about 2 ml of 0.01 M KMn, solution in a test tube. I added 2 ml of 1 butanol to it. I closed the test tube with a stopper and shook the contents of the test tubes I observed the colour of the permanganate solution over a period of five minutes with occasional shaking.
I repeated this test with the other two isomeric alcohols.
Observations :
Reagent 1 - butanol 2 - butanol 2- methyl-
2 - propanol
1. Sodium Bubbles of gas Fewer bubbles Fewer bubbles of
observed of gas gas (white solid
formed)
2. Conc. HCI No reaction No reaction Milky emulsion
evident evident formed
3. Neutral KMnO4 Bright colour Some colour Some colour
after first shaking change (deep change (Red) change (Red)
After 5 minutes Red) Liquid in two single layer
Brown ppt. seperate layers, upper A slight brown
Liquid forms two one pink, lower one ppt. settles.
layers, both clear is brown red
Inference : 30
2Na + 2ROH-H2+ 2RONa
2. With concentrated hydrochloric acid 2-methyl-2 propanol reacted producing a product of low solubility while other two isomers did not show any reaction. This indicates a less strong bond between the C and the OH in the compound where the carbon is bonded to three other carbons as in OH
CH3 -C- CH3
CH3
3. The reaction with neutral potassium permanganate showed that the primary and secondary alcohols were more easily oxidized. On consulting books on organic chemistry it was revealed that primary alcohols on oxidation give aldehydes and acids while secondary alcohols on oxidation give ketones.
Conclusion : On examining the ball-and-stick models of three isomeric alcohols with the formula C4H9OH and the chemical properties of the three isomers it can be concluded that there is a definite relationship between the structure and the properties of the alcohols which is as follows :-
1. In each location the O-H bond is broken in reaction with sodium, but this seems to occur most easily when the -OH is attached to a carbon atom which is bonded to only one carbon.
2. Cl is substituted for the -OH in an alcohol only when the -OH is on a carbon bonded to three other carbons.
3. A Carbon atom bonded to three other carbons was least succeptible to oxidation while the end carbon atom was most susceptible to oxidation.
By investigating the properties of hydrocarbons and different alcohols it was found that they show a variation in properties because of difference in their structures.
Extension of the Project : Look for the physical properties of the three alcohols in a standard book on organic chemistry and arrive at a relationship of the structure of the three alcohols and the trends in their properties.
Predication of the Properties : There is a fourth alcohol with the formula C4H9OH. Draw a structural formula for it and name it. How would you predict that it would react with :-
(a) Metallic Sodium.
(b) 12 M HCl.
(c) Neutral 0.01 M KMnO4.
References 1. J.D. Roberts, "Organic Chemical Reactions", Scientific American.
2. W-Hertz, "The shape of Carbon compounds", Benjamin, New York.
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