The purpose of this experiment is to find how the rate of hydrolysis of an organic halogen compound depends on: a. the identity of the halogen atom, b. the nature of the carbon-hydrogen 'skeleton'. Theory Halogen-compounds are organic compounds composed of carbon, hydrogen and halogen. One of the characteristic reactions of halogenoalkanes is nucleophilic substitution reactions.
A general equation for the nucleophilic substitution is: Nu- + R-X R-Nu + X-(where R = alkyl group, X = halogen atom) In this experiment, the rates of hydrolysis of 1-chlorobutane, 1-bromobutane, 1-iodobutane and chlorobenzene are compared. The nucleophile in this substitution is H2O. OH- attacks the carbocation and displaces a halide ion from the halogenalkane, which is called hydrolysis. A general equation for the hydrolysis is: H2O + R-X R-OH + X- As the halide ions substituted can be identified by silver nitrate solution, Ag+ (aq) + X- (aq) AgX (s).
The rate of reaction can be followed by time for the first appearance of precipitate. Since halogenoalkanes and halogenoarenes are insoluble in water while silver ions dissolve in aqueous solution, ethanol is added to the solution to act as a common solvent for halogeno-compounds and silver ions.
In this experimemt, the variables are: Controlled variables Independent variable Dependent variable Temperature Concentration and Volume of silver nitrate solution used Drops of Haloalkane/Halobenzene added, Volume of Ethanol used Species of Halogen compound used Time for the first appearance of precipitate Requirements Apparatus Safety spectacles ? 1 Bunsen burner ?
No comments:
Post a Comment