- Join over 1.2 million students every month
- Accelerate your learning by 29%
- Unlimited access from just £6.99 per month
AS and A Level: Organic Chemistry
Meet our team of inspirational teachers
Five equations you must know for organic chemistry
- 1 Alcohol + carboxylic acid = ester + water (eg CH3OH + CH3CH2COOH becomes CH3OOCH2CH3 + H2O)
- 2 Alkene + hydrogen = alkane (eg CH2=CH2 + H2 becomes CH3CH3)
- 3 Alkene + water = alcohol (eg CH2=CH2 + H2O becomes CH3CH2OH)
- 4 Halogenoalkane + hydroxide ion = alcohol + halide ion (eg CH3Br + OH- becomes CH3OH + Br-)
- 5 Alkene + hydrogen bromide = halogenoalkane (eg CH2=CH2 + HBr becomes CH3CH2Br)
Five facts about alcohols
- 1 Primary alcohols are oxidised into aldehydes and water, which are then oxidised into carboxylic acids. Secondary alcohols are oxidised into ketones and water. Tertiary alcohols cannot be oxidised.
- 2 Alcohols are oxidised by acidified potassium dichromate (H+/K2Cr2O7). This starts off orange and will turn green if it oxidises something (so with tertiary alcohols it will stay orange).
- 3 There are two ways of making alcohols: fermentation and hydration of alkenes. Fermentation is good because it uses renewable resources and does not take much energy, however it can only produce alcohol up to 14% before the yeast die.
- 4 Alcohols are soluble in water as they can make hydrogen bonds with the water. However, the “carbon chain” attached to the OH cannot interact with water and is insoluble. This means that alcohols become more insoluble the longer the carbon chain.
- 5 Alcohols have a very high melting and boiling point compared to alkanes of the same chain length. This is because they can form strong hydrogen bonds with each other that require a lot of energy to break.
Five facts about hydrocarbons
- 1 The longer the carbon chain the higher the higher the boiling point, as there will be more points of contact and stronger van der Waals forces.
- 2 The more branched the carbon chain the lower the boiling point, as the molecules will not be able to pack as close together and will have weaker van der Waals forces.
- 3 Hydrocarbons are insoluble in water as they cannot make intermolecular forces with them.
- 4 Hydrocarbons have low boiling and melting points as the only intermolecular forces that can hold them together are weak van der Waals forces which require little energy to break.
- 5 When processing crude oil (a hydrocarbon), the aim of the game is to get short, highly branched hydrocarbons. This will increase their volatility and make them a better fuel. We do this through: fractional distillation (sorts them into different sizes), cracking (splits long chains into short chains), isomerisation and reforming (makes the chains branched and cyclic).
In order to calculate the enthalpy change of Calcium Carbonate to Calcium Oxide, which is exceedingly hard to control and measure the energy change we must use Hess' law
With the enthalpy energy values for Calcium Carbonate and Calcium Oxide only then can we calculate the enthalpy change for Calcium Carbonate and Calcium Oxide. Enthalpy Calculations There are a few equations I must use to obtain my final answer firstly I must calculate the energy transferred in the reaction using the following equation:- Equation 1 Mass of liquid(g) x specific heat capacity of aqueous solution(Jg K ) x temperature rise(�C) = Energy Transferred (J) OR ?H = -M x Cp x ?T But this doesn't calculate the energy transferred per mole, to do this I must use:- Equation 2 = No.
- Word count: 1289
I have chosen the four alcohols as they have no or very few isomers, which will lead to more accurate results. These are the formulae for the alcohols I will be using: Methanol CH3OH Ethanol C2H5OH Propanol C3H7OH Butanol C4H9OH Plan Apparatus to be used: * My choice of alcohols (in the form of spirit burners) * A stand and clamp * A bomb calorimeter or metal cup * Thermometer (0.1 accuracy) * Electronic weighing scales (2 d.p. accuracy) * 100cm3 measuring cylinder (0.1 accuracy)
- Word count: 2258
To Investigate Whether There is a Link Between the Number of Carbon Atoms in Alcohol and its Standard Enthalpy of Combustion
The energy is given out when forming the bonds between the new water and the carbon dioxide molecules. Here are the balanced equations for the alcohols that I will be using: Methanol - CH3OH + 11/2O2 ? CO2 + 2H2O Ethanol - C2H5OH + 3O2 ? 2CO2 + 3H2O Propanol - C3H7OH + 41/2O2 ?3 CO2 + 4H2O Butanol - C4H9OH + 6O2 ? 4CO2 + 5H2O Pentanol - C5H11OH + 71/2O2 ? 5CO2 + 6H2O Hexanol - C6H13OH + 9O2 ? 6CO2 + 7H2O Heptanol - C7H15OH + 101/2O2 ? 7CO2 + 8H2O Octanol - C8H17OH + 12O2 ?
- Word count: 1128
The lid should be placed on to prevent any water being lost through evaporation before and after the heating. The equipment should then be set up as seen in figure 1. However before the draught shield is put in place calorimeter should be positioned exactly 10cm above the flame. This is to ensure that the same distance is present between each of the alcohols and the water that it is heating. Keeping this constant between different fuels ensures that the same amount of energy will be lost to the surroundings for each fuel.
- Word count: 3933
The three elements that will be used for this investigation are chlorine, bromine and iodine. Chlorine is a greenish yellow gas, which combines directly with nearly all elements. Chlorine is a respiratory irritant. The gas irritates the mucous membranes and the liquid burns the skin. Bromine is the only liquid nonmetallic element. It is a member of the halogen group. It is a heavy, volatile, mobile, dangerous reddish-brown liquid. The red vapour has a strong disagreeable odour, resembling chlorine, and is irritating effect to the eyes and throat. It has a bleaching action. When spilled on the skin it produces painful sores.
- Word count: 1398
The first four of the alcohols listed above have carbon chains with 1,2,3 and 4 Carbons. I chose to use these alcohols with an increasing number of carbon atoms in their carbon chains. The reason for this is I can investigate whether the change in the enthalpy of combustion increases by the same amount for every extra carbon in the carbon chain. I also decided to use octanol it has a carbon chain length of eight so it has twice as many carbons as butanol.
- Word count: 1420
For this experiment I have been given a task to determine which is the best Alcohol from its Homologous series. I can determine this by finding the Enthalpy change of Combustion for Alcohols.
Secondly, the temperature of the water also needs to be kept the same as well as the distance between the Crucible and the Sprit Burner. If the factors are not controlled then it will lead to the experiment being bias. The process in which I intend to avoid this from occurring is by controlling the temperature of the water using a thermometer and controlling the distance between the Crucible and Sprit Burner by measuring the distance using a 30cm ruler stick.
- Word count: 1448
The aim of this experiment is to investigate the enthalpy change of combustion for a variety of alcohols and determine how the number of carbon atoms affects the combustion of the alcohol.
However there are other chemicals, which are better fuels and are cheaper and are therefore more widely used. Unleaded petrol contains about 5% methanol the advantages of methanol are that it burns cleanly however it is more toxic than ethanol and produces less energy per litre than petrol. Ethanol is used as a fuel in the form of methylated spirit. This spirit burns with a light blue flame. Due to its volatiltity, which is explained below, the flame can be hard to detect in sunlight, so when filling stoves accidents can occur. However alcohols are relatively light therefore campers can prefer carrying these to other chemicals.
- Word count: 6616
Intermolecular forces are generally much weaker than covalent bonds. As the number of carbons increase the intermolecular force increases. However the more branches there are the weaker the intermolecular forces become. Isomers can also affect intermolecular forces; different physical properties of isomers can make the intermolecular forces stronger. The boiling points are determined by the strength of the intermolecular forces. So the stronger the intermolecular force, the higher the boiling point is. In alcohols, as the carbons increase then the intermolecular force should also increase.
- Word count: 2200
Classify as endothermic or exothermic: * NaOH dissolves in water & temp. of solution rises - Exothermic * Ammonium Chloride dissolves in water and temp. of surroundings drop - Endothermic * H and O combine explosively into water - Exothermic * Liquid water condenses into ice at 0 C - Exothermic * Liquid Nitrogen boils spontaneously at room temp.- Endothermic Why is standard enthalpy changes of combustion always negative? * Because heat is always evolved, the reaction is exothermic and therefore heat is lost to the surroundings. The energy required to break bonds is always less than the energy released when bonds are formed.
- Word count: 525
In using the calorimeter we need to know the specific heat capacity of water ( the energy needed to raise the temperature of 1g of water by 1 c). When the flame calorimeter is used, the energy transferred is found from Energy transferred E = m c ?T M represents mass of water C represents specific heat capacity of H2O T represents temperature Equipment Calorimeter Thermometer Measuring cylinder Ethanol/butanol Scales Set up Method I set up the equipment and filled my burner with the butanol and weighed it I also weighed the burner.
- Word count: 514
I am going to investigate the difference in enthalpy of combustion for a number of alcohols, the enthalpy of combustion being the'enthalpy change when one mole of any substance is completely burnt in oxygenunder the stated conditions'.
The measurements * Mass of alcohol burned (g) * Temperature increase (oc) will tell me what mass of alcohol is used during combustion to cause the temperature increase of 20oc in the water, I can then work out the energy released per mole and compare these values and see which has the highest enthalpy of combustion. I will need to repeat my experiment a number of times and take an average so I am sure of an accurate result. The set up of the apparatus that I plan to use is shown below The set up of the apparatus as you can see is very simple, the calorimeter, which contains the 100ml of water, is held directly above the spirit burner by a retort stand and clamp.
- Word count: 5612
The reactions that I am going to be looking at are all combustion reactions and are all exothermic reactions. This means that energy will be released during the reaction and more bonds will be formed than broken. It is possible to show a reaction and its ?H value in terms of a reaction path graph. Let us take the example of methane reacting with oxygen - a reaction not too dissimilar to the one that I will be carrying out.
- Word count: 2432
1. 10 cm3 of ethanol was added into an insulated 50 cm3 beaker by using a measuring cylinder. The temperature of the liquid was measured. 2. 20 cm3 of cyclohexane was added to the ethanol in the beaker. It was then mixed well and the lowest temperature attained was recorded. C. 1. 10 cm3 of ethyl ethanoate was measured into an insulated beaker. Its temperature was recorded. 2. This was added to 10 cm3 of trichloromethane and was mixed well. The highest temperature attained was recorded. D. 1. 10 cm3 of ethyl ethanoate was measured into an insulated beaker.
- Word count: 685
is the enthalpy change of combustion. Average bond enthalpies for elements in their gaseous states (kJmol-1): Carbon - Carbon (C-C) = +347 Carbon - Hydrogen (C-H) = +413 Oxygen - Hydrogen (O-H) = +464 Carbon - Oxygen (C-O) = +358 Carbon - Oxygen double bond (C=O) = +805 Oxygen - Oxygen double bond (O=O) = +498 Energy absorbed when bonds are broken (positive): (E=Energy) = E 3(C-H) + E (C-O) + E (O-H) + E 1.5(O=O) = 3(413) + 358 + 464 + 1.5(498)
- Word count: 2750
Combustion of methanol: test 1 * Mass of water = 60ml * Temperature difference = 68�C * Difference in weight of methanol = 2.2g * Weight of calorimeter = 65.4g * Specific heat capacity (SHC) of water = 4.17 Jg-1K-1 * SHC of copper = 0.38 Jg-1K-1 We have already established that the aim of this experiment is to investigate how and why the enthalpy change is affected by the molecular structure of the alcohol. To do so, you need to burn a certain alcohol under a calorimeter containing water and calculate the energy enthalpy change being discharged.
- Word count: 4837
This one is not used because it will just keep substituting the chemicals and you will end up with a huge range of compounds, most, if not all of which will not be needed. These products are called amines and an example of one would be CH3CH2NH2, which is ethylamine. The bond enthalpies of the 4 most reactive halogens is as follows Bond Bond enthalpy (kj mol��) C-F 467 C-Cl 340 C-Br 280 C-I 240 From this table you can see that bond enthalpy decreases going down the group.
- Word count: 794
Once my results have been obtained I will compare them against the theoretical enthalpy values. If they don't match up I will suggest some factors which conclude why. Hypothesis My hypothesis is that the more carbon atoms, the more heat will be produced. Alcohols produce heat when they burn in oxygen or air. Full combustion should generate only two products: CO2 and H2O. I predict that the alcohol with the greatest relative molecular mass will be the most efficient. Therefore, it will be Butan-1-ol as it has the greatest mass-per-mole of each of the four alcohols.
- Word count: 1010
The Relationship Between The Number of Carbon Atoms In An Alcohol And Its Standard Enthalpy Change Of Combustion.
It can also be seen that The RMM increases by 14 when the amount of carbons in the alcohol increase (1 carbon atoms + 2 hydrogen atoms = 12 + 2). * All that I have explained above is that of the first part of the aim of this experiment, the amount of carbon atoms in an alcohol. In order to carry out this experiment, I need to know two separate pieces of information, the first is the amount of carbon atoms in the alcohol, this, I have explained above and the second is the harder piece of information to find, this is the enthalpy change of combustion.
- Word count: 3052
For instance, if hydrochloric acid were to be used to acidify the sodium salicylic, then the sodium compound produced would be sodium chloride. https://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Salicylic_Acid.svg/2000px-Salicylic_Acid.svg.png https://www.emdmillipore.com/waroot/medium/567630%5b567630-ALL%5d.jpg + HCl ? + NaCl C6H4OHCOONa + HCl ? C7H6O3 + NaCl Sodium Salicylate + hydrochloric acid ? Salicylic acid + Sodium chloride (Brown, 2016) In effect, an acetylation is performed using the salicylic acid and acetic anhydride to produce aspirin and acetic acid (Brown, 2016). This process is deemed as an acetylation as an acetyl functional group (CH3CO) is integrated into the chemical compound of salicylic acid to produce acetyl salicylate (aspirin) (Brown, 2016).
- Word count: 5290
- Word count: 5290
The aim of this experiment was to recrystallise an impure sample of benzoic acid from hot water, and determine its purity through infra-red spectroscopy.
The beaker was then washed out with water several times and the remains were poured into the Buchner funnel. The glass rod was also rinsed and the remains were also transferred into the Buchner funnel. The crystals were then washed with cold water and left to dry for approximately 5 minutes. 6. A clean watch glass was then weighed and recorded using the four decimal point mass balance. As much of the crystals as possible were collected from the filter and transferred into the watch glass. The crystals and watch glass were then weighed and recorded together using a four decimal point mass balance.
- Word count: 1234
A spatula was used to insert anti-bumping granules into the boiler (these help the distribution of heat throughout the solvent). 4. 250cm3 of beer was measured and poured into the boiler by a funnel. 5. The boiler was placed into the flameless heater, which was switched on. 6. After some time, the beer began to boil, and vapours began to rise. The vapours pass through the fractional distillation column and into the condenser, where it cools down and turns back into the state of liquid.
- Word count: 759
Experiment. The aim of this experiment is to identify which substances are present in the flu medicine powder
Unknown tested for Phenylephrine +CuSO4: solution was cloudy to begin with. Changed colour from cloudy light green to yellow. +NaOH: solution turned dark green with yellow precipitate. +Ether: Formed three layers; clear, blue and yellow precipitate at the bottom. Ascorbic Acid test with Ag+ + Nitric Acid: solution turned from a white cloudy colour to yellow cloudy. + Silver Nitrate: solution turned into a dark creamy colour with silver precipitate. The purpose of testing Phenylephrine in this way is to see the reaction it has with Ag+. In this way you are able to determine whether the compound has an effect with the reaction with the unknown white powder.
- Word count: 830
Question: What is the change in enthalpy for magnesium after the reaction with vinegar? Hypothesis: If the magnesium reacts with vinegar then the change in enthalpy will be a very high value. Procedure: All materials were gathered and cleaned. The vinegar of 20 ml was measured using two 10 ml graduated cylinder to get a precise amount of vinegar. The vinegar was put into a Styrofoam cup. Another Styrofoam cup was put over the first cup for insulation. The piece of the magnesium was measured and recorded.
- Word count: 770