Hydrolysing Organic Halogen Compounds. The purpose of this experiment is to find out how the rate of the hydrolysis of an organic halogen compound depends on (1) the identity of the halogen atom (2) the nature of the CH skeleton.

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Victor Leung 7C (10)        Experiment Date: 28TH September, 2006.

EXP1 – Hydrolysing Organic Halogen Compounds

Aim:

The purpose of this experiment is to find out how the rate of the hydrolysis of an organic halogen compound depends on (1) the identity of the halogen atom (2) the nature of the CH skeleton.

Principle:

The hydrolysis of haloalkanes is an example of nucleophilic substitution in which the carbon halogen bond is replaced with a hydroxyl group. Water molecule is the nucleophile of the reaction while the halide ion departs as the leaving group. The reaction occurs faster with alcohol acting as a common solvent. The ease of leaving of halide ions increase in as the atom becomes bigger, and the bonding length longer.

Method:

The experiment made use of the product of hydrolysis – halide ions. The halide ions formed could be detected by AgNO3 which forms precipitation. The length of time required is inversely proportional to the rate of reaction. By observing the changes in the test tubes, we could compare the reactivity of the samples.

Apparatus and chemicals:

  • 1-chlorobutane , 1-bromobutane , 1-iodobutane , chlorobenzene;
  • Secondary Alkyl Halide (2° R-Cl), Tertiary Alkyl Halide (3° R-Cl)
  • Silver Nitrate (AgNO3)
  • New Clean Test tubes;
  • Clock

Experiment Procedure and Observations

  1. Six test tubes were prepared with 2cm3 of ethanol and 5cm3 of silver nitrate added into it.
  2. Six drops of the each of the six chemicals subjected to analyze are added into the test tubes.
  3. The test tubes were shook well and placed on a test tube rack.
  4. Times required for precipitates to appear were taken down.
  5. Observations were taken down.
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Results Recorded

#Water is present in all reactions from the AgNO3(aq) which acts as an reactant.

Calculations

No calculation is needed, visual compare only. Hurray!

Discussions

Introduction

The reactions involved are all nucleophilic substitution which involves SN1 and SN2 mechanisms. The reaction rate of the two reaction path ways determines by several factors which includes the structure of the substrate, the strength of the nucleophile and the stability of the leaving group.

In our experiment, all reactions involve water acting as the nucleophile; the lone pair electrons of the oxygen atom seek an electron deficient site to attack. ...

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