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

Identification of an unknown organic compound.

Extracts from this document...


A2 Chemistry coursework: Identification of an unknown organic compound. Test wit Brady's reagent. Test identifies: the presence of a carbonyl group (aldehyde or ketone) Apparatus: * Test tube * Brady's reagent * Pipette Method: pipette a few drops of Brady's reagent into the test tube containing the unknown compound. Observation: * Colour change to a yellow/orange implies that a carbonyl group is present. * No colour change suggests that a C=O functional group is not present which implies that the unknown compound is any of the other six unknown organic compounds. Diagram: Explanation: * 2, 4 dinitrophenylhydrazine reacts with the carbonyl group to form products known as 2,4 dinitrophenylhydrazones. * This is a nucleophillic addition-elimination, as a water molecule is eliminated from the carbonyl group and 2 hydrogens from the hydrazine. * As this happens, the 2 compounds form a link to produce 2,4 dinitrophenylhydrazone. As the product forms an orange/yellow precipitate should form. * However if the carbonyl group is not present then no reaction takes place. This is because an oxygen atom needs to be present for a water molecule to be removed, which causes the formation of 2,4 dinitrophenylhydrazone. Safety: * Sulphuric acid is corrosive, avoid contact with skin. * Wear gloves at all times. * Keep goggles on at all times. * Brady's reagent is very harmful when inhaled or ingested, avoid contact with mouth and avoid inhalation of fumes. ...read more.


The other Br - ions bonds with the carbon with the + charge. It is due to this that bromine decolourises which shows the presence of a C=C bond. Phenol: Electrophillic substitution occurs as Phenol reacts with bromine. Because of instantaneous dipoles, the bromine atom with + is attracted to the delocalised ring from the phenol. A bond is formed with the phenol and Br leaving the other Br as an ion as it gains an electron. As this happens the ring becomes unstable, so it needs an electron to regain its stability. This is done by the phenol losing a hydrogen ion which bonds with the bromide ion to give HBr (hydrogen bromide). This occurs three times in total. 2,4,6 tribromophenol and 3 molecules of hydrogen bromide are produced when 3 molecules of bromine react with phenol. This happens as 4 hydrogen atoms are replaced by 3 bromine atoms on the aromatic ring. As this happens the bromine decolourises and a white precipitate is formed. Safety: * Wear goggles at all times. Bromine water is irritating to the eyes. * Bromine water is harmful when inhaled or ingested. Seek medical advice immediately if ingested. Test with sodium hydrogen carbonate. Test identifies: the presence of a carboxylic acid. Apparatus: * Conical flask * Limewater * Sodium hydrogen carbonate * Test tube * Gas jar * Delivery tube Method: Add sodium hydrogen carbonate to the solution of the unknown compound and collect gas, if any that is given off and then bubble it through limewater. ...read more.


Pop test- if hydrogen is present, when a lit splint comes in contact with the gas in the test tube; a squeaky noise (pop) is made. Observation: When the lit split enters the tube with the gas, if a squeaky pop noise is made then hydrogen is present. This presence of hydrogen comes from the reaction between the alcohol and sodium. This determines the presence of a tertiary alcohol. However if no hydrogen is given off, then no squeaky pop noise is made as a lit splint enters the tube. This means that a tertiary alcohol is not present; meaning that the unknown compound is an ester, because this is the only remaining unknown organic compound. Explanation: Hydrogen is produced when an alcohol and alkali metal react. The following reaction: Hydrogen being given off is an indication of sodium and the alcohol reacting. The gas which is collected is tested with a lit splint to determine whether the gas is hydrogen or not. Esters do not react with hydrogen, so no hydrogen is given off. If the pop test is negative, no pop noise is made; it means that a tertiary alcohol is not present, thus the unknown can only be an ester as all the other organic compounds have been eliminated. Safety: * Sodium is corrosive. Wear gloves at all times and avoid contact with skin. * Sodium is also harmful if ingested. * Wear goggles at all times. * Sodium is highly reactive when in contact with water and air. * Sodium is highly flammable, avoid contact with fires. ...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)

    5. Oxidation with acidified dichromate (VI) solution Aldehyde can be further oxidized to carboxylic acid. The product formed will be a carboxylic acid. In the reduction of dichromate ion, the dichromate ion (orange) is turned to chromium ion (green). Ketone may undergo further oxidation to form carboxylic acid with hot acidified potassium permanganate and under reflux.

  2. Identification of an Unknown Organic Compound

    Always work in the fume cupboard because inhaling the fumes can damage the respiratory system. Seek immediate medical attention if any contact with the chemical is made.ii * Acetone is only very slightly toxic and not much harmful. If an eye or skin contact is made then rinse with water immediately.

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

    So this will affect my results for the enthalpy change of combustion because all the fuel was not transferred to the water. There were aspects of my procedure that were used to try and combat these errors to ensure as accurate and reliable results as possible.

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

    * 100 cm3 conical flask * Distilled Water * 10 cm3 pipette * 100 cm3 beaker * Hirsch funnel * Water bath containing crushed ice * Goggles * Laboratory coat * Analytical balance ( 4 d.p) Apparatus Justification * Salicylic acid - contains the -OH group, which will react with the acid anhydride to produce acetylsalicylic acid.

  1. Comparing the enthalpy changes of combustion of different alcohols

    x 100 = 0.30% Water used: 100g; Percentage uncertainty: (0.05/100) x 100 = 0.05% Temperature difference: 15.20�C Percentage uncertainty: (0.05/15.20) x 100 = 0.32% Total error = 0.30 + 0.05 + 0.32 = 0.67% 2nd Recording Mass of fuel used: 1.60g; Percentage uncertainty: (0.005/1.60)

  2. Investigating the Enthalpy Changes of Combustion of Alcohols.

    There are no heal losses to surrounding air, because there is no surrounding air, just water. The heat can only escape through the water. Secondly, the combustion occurs in a pressurised oxygen atmosphere, preventing incomplete combustion. The significance of incomplete combustion is discussed in the next appendix.

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

    The change in temperature using this method was much greater and easier to measure. It was also a lot more accurate as less heat was lost into the surroundings and from the copper calorimeter. I therefore decided to carry out this experiment fully using this method using at least four

  2. Esterfication. he purpose of this lab is to achieve a specific odour through ...

    Observations: Substance State Colour Scent Alcohol - liquid - clear - strong and unpleasant Acid - solid (powder) - white - strong and unpleasant Ester - liquid - two layers -clear (slightly opaque) - ripe cherry Extension Questions: 1. The purpose of H2SO4 in this lab was to be a

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