• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13

Preparation of haloalkane. The purpose of this experiment is to prepare 2-chloro-2-methylpropane from methylpropan-2-ol

Extracts from this document...


Date: 20/9/2011 Exp. No.: 21 Title: Preparation of a halogenoalkane Aim: The purpose of this experiment is to prepare 2-chloro-2-methylpropane from methylpropan-2-ol Introduction: In this experiment, 2-chloro-2-methylpropane will be prepared from methylpropan-2-ol and hydrochloric acid. This reaction takes place at room temperature as methylpropan-2-ol is a tertiary alcohol which undergoes substitution very readily. Zinc chloride could be added to be a catalyst to increase the reaction rate, but for tertiary alcohol the reaction rate is already fast enough. The equation of the reaction is: The synthesis is a nucleophilic substitution reaction. The OH group is being substituted by a chlorine ion. Purification process includes removal of acid, dehydration and distillation. The product is purified by using the separation and removing the excess HCl with saturated sodium hydrogencarbonate solution followed by dehydrating with anhydrous sodium sulphate and finally distillation. Apparatus and chemicals: Apparatus: Separation funnel with stopper, 10cm3 and 25cm3 measuring cylinders, electronic balance, stands and clamps, 0-100oC thermometer, quick-fit apparatus for distillation, Bunsen Burner, tripod, wire gauze, boiling tubes with stopper, anti-bumping granules, safety spectacles Chemicals: 9cm3 of 2-methylpropan-2-ol 2g of anhydrous sodium sulphate granules 20cm3 concentrated hydrochloric acid 10cm3 saturated sodium hydrogencarbonate solution Precautions: 1. 2-chloro-2-methylpropane and 2-methylpropan-2-ol are flammable. So, these liquids must be kept away from direct flame. Flammable 2. Concentrated hydrochloric acid is very corrosive and there are HCl fumes above the concentrated HCl solution, so we should wear safety spectacles during the whole experiment and transfer of acid should be done in fume cupboard. ...read more.


1. Concentration of nuclephile Substitution is preferred when a concentrated nucleophile is used. In this experiment, concentrated acids were used, so the concentration of the nucleophiles is very high which favours elimination. 2. Temperature High temperature favours elimination reaction, that is one of the reasons why we add concentrated HCl little by little instead of adding 20cm3 altogether, as the reaction is exothermic which release larger amount of heat, then the rate of reaction of elimination may increase (although it is still very slow). The other reason for adding concentrated HCl little by little will be discussed later. 3. Distillation of cyclohexene from the reaction mixture when it was formed. This is important because the cyclohexene formed may react with water to form back cyclohexanol. Using high temperature can ensure that cyclohexene reaches its boiling point immediately after formation and being distilled out. 4. Polarity of the solvent. Low polarity solvent favours elimination which high polarity solvent favours substitution. In this experiment, we used water as a solvent which is of a high polarity, so this increases the rate of substitution. 5. Structure of the reactant 3o carbon increases the stability of the carbonium ion formed in the intermediate. With the SN1 pathway, a carbonium ion is formed as an intermediate. The carbonium ion has higher stability with a tertiary carbon because of inductive effect. R groups (CH3 in this experiment) ...read more.


3. We were only using a measuring cylinder to measure each reagent, which was not quite accurate. Therefore, there might be a maximum error of 0.25cm3 as the measuring cylinder only had markings every 0.5cm3. When that measuring cylinder was used to measure 9.0cm3 of 2-methylpropan-2-ol, the maximum percentage error was � 100% = 2.78% In addition, the measuring cylinder was used to measure volumes 3 times. This might contributed quite a lot on the error in this experiment. Further experiments: Adding AgNO3 solution With a little bit of left-over product (2-chloro-2-methylpropane) in a boiling tube, a few drops of AgNO3 were added into the boiling tube to test for whether the product is a halogen compound. After adding the AgNO3 solution, white ppt. was formed which confirmed that the product was actually a chloro compound. This can be confirmed as AgCl(s) is white in colour, AgBr(s) is pale yellow, while AgI(s) is yellow. After the ppt. was formed, the boiling tube was brought to direct sunlight. This caused the white ppt. to turn grey and slightly purple. This was actually a thermal decomposition and the equation is: 2AgCl 2Ag + Cl2 White Grey The product was slightly purple because the silver was not evenly deposited. There were many cavities which diffracts lights, so a slightly different colour may be observed. However, this test is slightly not too accurate because carboxylic acids have been known to react in this test, giving false positives. Reference: http://chemistry2.csudh.edu/rpendarvis/SN1Elim.html http://www.chemguide.co.uk/mechanisms/nucsubmenu.html http://www.chemtube3d.com/Elimination%20-%20E1.html http://www.chemhelper.com/e1.html http://www.wellesley.edu/Chemistry/chem211lab/Orgo_Lab_Manual/Appendix/ClassificationTests/halide.html http://www.chem.ucla.edu/~bacher/General/30BL/tips/Sepfunnel.html http://en.wikipedia.org/wiki/Tert-Butyl_chloride http://en.wikipedia.org/wiki/Silver_chloride http://www.sciencelab.com/msds.php?msdsId=9927134 http://www.organic-chemistry.org/namedreactions/nucleophilic-substitution-sn1-sn2.shtm http://www.chem.ucla.edu/~bacher/General/30BL/tips/Sepfunnel.html ?? ?? ?? ?? ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Organic Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Organic Chemistry essays

  1. Marked by a teacher

    Reactions of aldehydes and ketones. The purpose of this experiment is to compare ...

    5 star(s)

    than hydroxide ion, so the methoxide ion will take a proton from water forming an alcohol and leaving a hydroxide ion. However, depending on the reactivity of the nucleophile, there are two possible general scenarios: Strong nucleophiles (anionic) add directly to the C=O to form the intermediate alkoxide.

  2. Marked by a teacher

    Experiment to Determine Acidities of Wine. The purpose of this experiment is to ...

    5 star(s)

    From this, a pH against volume titration curve could be plotted and from this the fixed acidity of the wine could be calculated. The volatile acidity of the wine could then be calculated by subtracting the concentration of the fixed acids from the concentration of the total acids.

  1. The preparation of cyclohexene from cyclohexanol

    This whole setup was clamped. 5. 2 rubber tubes were connected to condenser's water in (near the head) and the water out (near the tip). 6. Finally a clean & dry conical flask (put in the ice bath) was placed to near the tip of the condenser to collect the distillate.

  2. The aim of this experiment is to produce Aspirin. This is an estrification in ...

    * Laboratory coat - Used to protect the skin and clothing. * Analytical balance- used to way the salicylic acid accurately to 4 decimal places. Results obtained were recorded in a table format:- Results Compound Theoretical yield (g) Actual yield (g)

  1. The aim of this experiment is to investigate the enthalpy change of combustion for ...

    When I calculated the bond enthalpies of both alcohols the result was the same so I felt my prediction was justified. However from looking at the results I recorded on both graphs I no longer agree with my prediction as both of the graphs tell the same story and show

  2. The Preparation of 1-bromobutane

    Reflux condenser 13. Guard tube containing soda lime 14. Small Bunsen or electric heating mantle Risk Assessment Chemical Hazard Corrective plan Butan-1-ol Harmful/flammable - avoid contact with skin - wear lab coat - if spilled clean up area with cold water - keep far away from Bunsen flame - wear eye protection.

  1. The aim of this experiment is to obtain the rate equation for the reaction ...

    4 0 [Propanone] /mol dm-3 0.4 0.8 1.2 0.4 0.4 0.4 0.4 [I2]/ mol dm-3 0.004 0.004 0.004 0.008 0.002 0.004 0.004 [H+]/mol dm-3 0.4 0.4 0.4 0.4 0.4 0.8 1.2 13. The propanone solution was poured into the solution in the boiling tube and the stopwatch was started immediately.

  2. Comparison between Cyclohexane and Cyclohexene

    The bromine water test is one of the chemical tests to differentiate alkanes and alkenes. In a test tube of cold acidified potassium manganate (VII), a type of oxidizing agent with cyclohexene, cyclohexa-1,2-diol is formed with the disappearance of purple colour of the acidified potassium manganate (VII).

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work