Comparing the rates of hydrolysis of chloro-, bromo- and iodo- alkane
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Introduction
Experiment2 Aim A. To compare the rates of hydrolysis of chloro-, bromo- and iodo- alkane. B. To compare the rate of hydrolysis of aliphatic and aromatic halogeno-compounds. C. To compare the rate of reaction of halogen ions under sunlight and when ammonium hydroxide is added. Procedure A: 1. 2cm3 of ethanol were added to three separate test tubes and were placed them in a beaker of water kept at about 60?. 2. 1 cm3 of 0.1M silver nitrate(V)solution was added to each test tubes. 3. Using separate teat pipettes, 5 drops of 1-chlorobutane was added to the first test tube, 5 drops of 1-bromobutane was added to the second and 5 drops of 1-iodobutane was added to the third. ...read more.
Middle
C: 1. 2cm3 of 0.1M silver nitrate(V)solution was added to three test tubes 2. 2cm3 of KCl, KBr and KI were added to the three test tubes respectively. 3. Half of each test tube was added to another test tube. 4. One set of test tubes were placed under sunlight, while the other set was kept in room and 2 cm3 of ammonium hydroxide was added. 5. The precipitate formed in each case was noted. Result A: Rate color Precipitate? 1-chlorobutane No obvious change 1-bromobutane Less fast cream White 1-iodobutane fastest yellow Yellow B: Room temperature 60? 1-bromobutane Turned unclear Fastest reaction, turned cream with white precipitate bromobenzene No obvious change No obvious change C: Without sunlight, ammonium hydroxide was added observation AgCl White precipitate and ...read more.
Conclusion
3. Compare the effect of the phenyl group have on the rate of the hydrolysis reaction, the haloalkane is more reactive than the halobenzene. The steric repulsion of the substituents in the 5-bonds transition state of the carbonium ions raises energy and slows down the reaction effect in the halobenzene 4. The reaction is likely to be faster if ethanol is replaced by NaOH because OH ions in NaOH(aq) has negative charge while H2O has only lone pair, but in fact NaOH will react with AgNO3 and the solution will turn green. 5. AgNO3(aq) acidified with HNO3(aq) plus carbonate because 2Ag+(aq) + CO32-(aq) --> Ag2CO3(s) H+ removes Ag2CO3(s) ...read more.
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