• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

To investigate the effect of the halogen atom on the rate of hydrolysis.

Extracts from this document...


Background knowledge The halogenoalkanes are a vital homologous series, this is due to their importance in organic synthesis, since the halide ion, X-(aq) is an excellent leaving group and may be readily substituted. Halogenoalkanes exist as simple molecules. Between these molecules, van der waals forces as well as dipole- dipole attractions (resulting from the polar C-X bond) operate. The existence of the dipole-dipole attractions explains why halogenoalkanes have slightly higher melting and boiling points when compared with the corresponding alkane. The general formula for halogenoalkanes is: CnH2n+1X. * Where X= fluorine, chlorine, bromine or iodine. Types of halogenoalkanes * Primary (1�) a halogen is present at the end of the chain: * Secondary(2�) a halogen is present in the body of the chain: * Tertiary(3�) a halogen is present at a branch in of chain: Strength of bonds I have included a table of the carbon - halogen bond energies, in which you can see trends between them. The main trend that you see is that the bond energies decrease from Fluorine to Iodine. With that in mind one can predict that due to the shared electrons being closer to the nucleus in fluorine than iodine, iodo-compounds will have the weakest bonds and greatest reactivity while fluorine compounds will have the strongest bonds and least reactivity. ...read more.


* Make sure the area around you is kept tidy and uncluttered so spillage does not occur, or that you trip or fall during the experiment. * Ethanol is highly flammable. Do not have any naked flames near the tubes or ethanol bottle. * The bromobutane and iodobutane is harmful therefore you must take care when handling these substances. * Clean your work area at the conclusion of each lab as directed by your teacher. * Know the location of all safety and emergency equipment used in the laboratory, immediately report any accident or hazard to your teacher Apparatus: * Safety glasses * Test tube rack * 4 test tubes * labels * 250 cm� beaker * 0�C - 100� C thermometer * 10 cm� measuring cylinder * digital timer * 3 dropping pipettes * 1-cholobutane* * 1-bromobutane* * 1-iodobutane* * ethanol * silver nitrate solution (approximately 0.1 mol dm- �) * use separate pipettes for each bottle of those indicated above with asterisks Method * Collect all apparatus on the list above. * Set up three test tubes in a test tube rack. Label each tube with 1 cm� ethanol. Add to the label of the first test tube 2 drops of 1-chlorobutane, to the second add 2drops of 1-bromobutane and to the third add 2 drops of 1-iodobutane. ...read more.


Furthermore, I predict that this precipitate will be either silver chloride, silver bromide or silver iodide depending on the halogenoalkanes used and as these precipitates will be formed at different rates the "crosses" on each test tube will disappear at different times. I predict that as the halogen is changed down the group, i.e. from chlorine to bromine to iodine, the rate of reaction will increase. This is because of the bond enthalpy of a carbon- iodine bond being lower in energy than that of a carbon-bromine bond, which is subsequently lower than that of a carbon-chlorine bond. This shown by the following extract from the website- http://www.webelements.com/webelement/text/c/enth.html C-X Bond Bond Enthalpy kj mol-� C-Cl 397� 29 C-Br 280�21 C-I 209�21 The enthalpies of the C-X bonds decrease from C-Cl to C-I due to the difference in size of the halogen atoms. As group 7 is descended, the size of the halogen atom increases, i.e. iodine is a much larger atom than chlorine. The larger the halogen atom is the less the bond overlap with the carbon atom, resulting in a longer C-X bond. The longer the bond the weaker the bond is and this means less energy is required to break the long carbon-iodine bond than the short carbon-bromine or even shorter carbon-chlorine bonds. Therefore I predict that iodine will be displaced in the least amount of time, followed by bromine and then chlorine. ...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. Comparing the rates of hydrolysis of chloro-, bromo- and iodo- alkane

    The test tubes were shaked and the order in which the precipitates appeared was observed. The precipitate formed in each case was noted. 5. Step1~4 was repeated while the test tubes were kept in room temperature.

  2. Free essay

    effect of carbon dioxide on rate of photosynthesis

    distilled water, which must be filled to the line that is etched on the neck of the volumetric flask. Make sure you check that the solution is jus bellow the curved meniscus at eye level. * Fill a large beaker with distilled water * Set up the apparatus as shown

  1. F336- aspirin individual Investigation

    May cause skin rash and eruptions. CARE The chromatography solvent is harmful by inhalation (as are the vapours produced by this activity) and highly flammable. Work in a fume cupboard or in a well-ventilated laboratory as directed and avoid inhaling the fumes. Avoid naked flames. The chromatography solvent contains cyclohexane.

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

    The total bond energy for these bonds is 1914KJ/mol. These are the extra bonds, which are being broken, and are therefore the endothermic increase when the carbon chain length is increased by one. When the chain length is increased by one the extra bonds formed are 2(C=O)

  1. Find the enthalpy change of combustion of a number of alcohol's' so that you ...

    I have also identified another trend from my results. I have noticed that as the molecular structure of the alcohol increases the moles of fuel burnt decreases. An example is the average moles of fuel burnt for ethanol is 0.056086956 moles but for Propan-1-ol it is 0.036611111 moles of fuel burnt.

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

    of aspirin that reacted lies between the following values, So therefore the confidence limit lies between 1.621 + 1.349 Melting point apparatus Percentage error = 0.10x 100 = + 0.10% 100 Total percentage error = + 0.10% Preparation of 0.1 mol dm-3 sodium hydroxide solution Balance error Percentage error = 0.00005 x 100 =+ 0.0025% 2.0000 Volumetric flask (class B)

  1. Planning Coursework - Investigation of rate of hydrolysis of halogenoalkanes

    To ensure the stopwatch is stopped at a right end points. It is decided to place a block paper at the back of the test tube such that if the colour of the paper cannot be seen, this refers that the precipitate has formed completely and will be the end point of the reaction.

  2. Rates of Halogenoalkanes

    + H2O (l) = C4H9OH (aq) + HI (aq) Equation of reaction with aqueous silver nitrate solution: hydrogen iodide + silver nitrate = silver iodide + nitric acid HI (aq) + AgNO3 (aq) = AgI (s) + HNO3 (aq) Predictions: Firstly I predict that during warming, reactions will occur in all test tubes except the control.

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