An example of a primary halogenoalkane would be 1-bromobutane:
H³C-CH²-CH²-CH²-Br
All of the C-X bonds are polar, the bond enthalpy’s for a C-F bond is 467Kj/mol, for a C-Cl bond is 340Kj/mol, for bromine it is 280Kj/mol and for iodine it is 240Kj/mol. These numbers reefer to the amount of energy in kilorjewls taken to break he bonds, I got this information from the AS CHEM WORKBOOK. From this information I know that the Fluorine bond is the most electronegative and the strongest bond and the iodine the least electronegative and therefore the least strong bond as the strength of a bond is determined by its elecronegativity.
I will only use chlorine, iodine and bromine as fluorine is such a strong reactant we will not be able to break the bond between it and the carbon atom. Hence iodine, the weakest bond reactive, will react the fastest because its bond will be broken easily, then bromine and the chlorine.
In this experiment I am investigating the rate of reactions for the Halogenoalkanes.
I know that one mole of C4H9X plus one mole of OHˉ will give me one mole of butanol and on mole of Xˉ I can use this information to determine how completed the reaction is at any given point in time. I do this by taking a sample of my reaction stopping (or at least dramatically reducing) the rate of reaction and adding an indicator and titrate that will show me how much OHˉ or Xˉ there is in the sample therefore showing how reacted it is. The faster reaction will have the least amount of acid or the most amount of Xˉ.
I will keep the test fair by firstly carrying out the reaction in a water bath to keep the temperature constant and using the same amounts and concentrations o reactants. The alternative would be to calculate the rates of reaction by using silver nitrate as an indicator this changes colour in the experiment. I would set up controls for each experiment and timed how long it will take for the test to get to the same state as the control. This is not very accurate as the colours for each are different and for chlorine it would go white this is not a good colour to spot. The molar method is a lot more accurate and although more Complex.
I will use the silver nitrate method to carry out the experiment. This is because it is simple and will still show which reaction is the fastest. The silver nitrate is in solution this means I will not have to add any water to the experiment and the reactions will all happen as one step rather then the hydrolysis followed by the titration.