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

Identifying an Unknown Compound

Extracts from this document...

Introduction

Identification of an Unknown Organic Compound Ensure a lab coat, safety glasses and gloves are worn during the experiments and work in a ventilated area. For all experiments test tubes and pipettes will be required. ALKENES: Alkenes contain a double carbon-carbon bond. APPARATUS: Unknown compound, bromine water. METHOD: Add 5 drops of bromine water to a test tube containing 1cm3 of the unknown and shake. OBSERVATION: Bromine water will decolourise from orange. EXPLANATION: The alkene decolourises bromine water and produces 1,2-dibromoethane. The double bond allows electrophilic addition reactions to occur. HAZARDS: Bromine vapour released from the water is 1^harmful^1 (see appendix). ESTERS: Esters are sweet- smelling products from reactions between carboxylic acids and alcohols. APPARATUS: Unknown compound, phenolphthalein, water bath, NaOH. ...read more.

Middle

Phenol- 3^corrosive^3 and 4^toxic^4. CARBOXYLIC ACIDS: Carboxylic acids are products of the oxidation of a primary alcohol or an aldehyde. Their functional group is -COOH. APPARATUS: Unknown compound, water, limewater, NaHCO3. METHOD: 3Add water and NaHCO3 to the unknown compound.3 OBSERVATION: Effervescence occurs after NaHCO3 is added; test the gas with limewater and it will go cloudy. EXPLANATION: Carboxylic acids although weak acids react like any other acid and undergo the same reactions. So CO2 is produced when reacted with NaHCO3. HAZARDS: NaHCO3- 2^irritant^2. CARBONYL COMPOUNDS: Carbonyl compounds consist of the C=O bond, examples are aldehydes, ketones and esters. However the 2,4-DNPH test is only positive for aldehydes and ketones. APPARATUS: Unknown compound, 2,4-DNPH. METHOD: Add 5 drops of 2,4-DNPH to the unknown in a test tube. OBSERVATION: A deep yellow/ orange precipitate appears. EXPLANATION: 4See diagram below. ...read more.

Conclusion

The orange dichromate (VI) ion, Cr2O72-, is reduced to green chromium (III), Cr3+. If the solution has remained orange it proves the presence of a tertiary alcohol as they cannot be oxidised.6 Another test can be carried out to confirm the presence of a tertiary alcohol, it is known as Lucas' test. APPARATUS: Lucas' reagent: a solution of ZnCl2 in concn HCl. METHOD: Add 2cm3 of Lucas' reagent to 1cm3 of the unknown and shake. OBSERVATION: A cloudy emulsion may be seen rapidly or no reaction may occur after 5 minutes. EXPLANATION: 7The reagent dissolves the alcohol and removes the OH group leaving a carbocation. The cloudiness is caused as the carbocation reacts with Cl- forming a chloroalkane. Tertiary alcohol is present if the emulsion forms rapidly and a primary alcohol if no reaction occurs.7 HAZARDS: K2Cr2O7- 4^toxic^4 and 6^oxidising^6. H2SO4- 1^harmful^1 and 3^corrosive^3. Lucas' reagent- 4^toxic^4 and 3^corrosive^3. ...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)

    After pouring away the solution, there were white solid crystal remaining in the test tube. 5. For propanone, there wer 2 colourless immisible layers formed. 6. Both of the solution became turned warm. Part 2 Treating with 2,4-dinitrophenylhydrazine 7. 2,4-dinitrophenylhydrazine solution was yellow in colour.

  2. Determination of the formula of Hydrated Iron (II) Sulphate crystals

    This would help to ensure I did not add too much or too little KMnO4. Also, if a powdered form of iron (II) sulphate was used then the container used to dissolved all the iron sulphate with the water and acid would not need to be used.

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

    heat absorbed by the water in joules, meaning it will improve the accuracy of the enthalpy change of combustion values. The thermometer may have contributed to the errors because its degree of accuracy was 0.50C. This may have affected my results by making a lower reading for the enthalpy change of combustion value.

  2. Investigation of Unknown compound

    Drop by drop; add ammonia solution until the precipitate of silver oxide nearly dissolves. Add a few drops of unknown to the tube and shake gently. Place tube in a beaker of warm water, note observations and immediately rinse out test tube.

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

    This suggests that the re-crystallised aspirin is pre with very little impurities. However if impurities are present, forward titration will neutralise acetylsalicylic acid and the impurities as well. Also using this titration it was difficult to identify the end point because aspirin is a weak acid and the reaction takes place very slowly.

  2. Qualitative Analysis (A combined approach using spectroscopic and chemical analysis for structural identification of ...

    For BL: In the hydroxamate test, after the addition o ferric chloride , a reddish brown colour was formed. The result was between positive and negative. When this test was repeated, a red-blue colour was formed which was a positive result.

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

    I also calculated the gradients of each of the individual graphs to calculate the increase in temperature per second for each of the alcohols. Butan-1-ol has the largest gradient of 0.39 degrees/second as I would have predicted. This is the most exothermic of the combustion reactions with alcohols and therefore the temperature increases in a shorter period of time.

  2. investigating the amount of ascorbic acid present in fruit

    It shows my best three titres which are in 0.1cm3 of each other. Titration (cm3): 1 2 3 Initial Burette Reading (cm3): 0.00 0.00 0.00 Final Burette Reading (cm3): 36.30 36.30 36.40 Titre (cm3): 36.30 36.30 36.40 Average Results Table (lime): This is the average table of results showing my average titres for the lime.

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