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

Comparison of Reactions of Aldehydes and Ketones

Extracts from this document...


1. Title Comparison of Reactions of Aldehydes and Ketones 2. Aim The purpose of this experiment is to compare the reaction behaviour of ethanal and propanone towards nucleophilic addition, condensation, alkali, oxidation and iodoform test. 3. Results & Calculations Rx Test Observations Ethanal Propanone A Addition reaction with sodium hydrogensulphate White crystal White crystal B Condensation reaction with 2,4-dinitrophenylhydrazine Yellow precipitate Orange precipitate C Reaction with alkali D Oxidations : I) acidified dichromate(VI) II) Tollens' reagent III) Fehling's solution Orange solution turns green No observable change Silver mirror No observable change Red precipitate No observable change E Iodoform test Yellow precipitate No observable change 4. Discussion A: This reaction works well for aldehydes. In the case of ketones, one of the hydrocarbon groups attached to the carbonyl group needs to be a methyl group. Bulky groups attached to the carbonyl group get in the way of the reaction happening. The aldehyde or ketone is shaken with a saturated solution of sodium hydrogensulphite in water. Where the product is formed, it separates as white crystals. ...read more.


till it forms precipitate and NH4OH was added till the precipitate is disssoved so thus formed mixture is known as Tollens' reagent. Once it has been identified that there is a carbonyl group on the organic molecule using 2,4-dinitrophenylhydrazine(also known as Brady's reagent or 2,4-DNPH), Tollens' reagent can be used to ascertain whether the compound is a ketone or aldehyde. Importantly, there is a special case in which Tollens' Reagent will give a positive for a ketone. If the ketone is an alpha-hydroxy ketone, then the Tollens' reagent will react. When adding the aldehyde or ketone to Tollens' reagent, the teat tube is put in a warm water bath. If the reactant under test is an aldehyde, Tollens' test results in a silver mirror. If the reactant is a ketone, it will not react because a ketone cannot be oxidized easily. A ketone has no available hydrogen atom on the carbonyl carbon that can be oxidized - unlike an aldehyde, which has this hydrogen atom. The reagent should be freshly prepared and stored refrigerated in a dark glass container. ...read more.


RCOOH + -CX3 � RCOO- + CHX3 5. Answers to Question 5.1Describe how Tollens' reagent can be prepared. Write a balanced chemical question for the reaction between Tollens' reagent and ethanal. Tollens' reagent needs to be prepared fresh by adding a drop of dilute sodium hydroxide to aqueous silver nitrate to give a brown precipitate of silver oxide. The precipitate is dissolved by adding concentrated ammonia to give the reagent, [Ag(NH3)2]NO3 (aq): 5.2Consider the mechanism of nucleophilic addition reaction to unsaturated carbonyl group, predict and explain the relative reactivity of ethanal and propanone. Reactivity of the ethanal is higher than that of propanone. Unlike the non-polar and electron rich carbon double bond, C=O double bond has a positive centre and undergoes nucleophilic addition. More positive on carbon, so it is more vulnerable to nucleophilic attack. Ethanal is more reactive than propanone since electron donating group of R makes the carbon in C=O in propanone less positive, less attractive to the nucleophile. Moreover, steric hindrance of two bulky R groups in propanone prevents the attack of the nucleophile on C=O 6. Conclusion Ethanal is more reactive than propanone in the following chemical reaction such as nucleophilic addition, condensation, alkali, oxidation and iodoform test. ...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 Physical 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 Physical Chemistry essays

  1. Double Displacement Reactions

    Clear 45 Na2CO3 Cu(NO3)2 Yes White Blue 46 Ca(NO3)2 Ca(NO3)2 No Clear 47 Ca(NO3)2 Na2PO4 Yes Blue Clear 48 Ca(NO3)2 NaBr No Clear 49 Ca(NO3)2 Zn(NO3)2 No Clear 50 Ca(NO3)2 K2CrO4 Yes Red Orange 51 Ca(NO3)2 FeCl3 Yes Peach Clear 52 Ca(NO3)2 NaOH Yes Blue Clear 53 Ca(NO3)2 MgCl2 No

  2. Investigating the rate of reaction between peroxydisulphate(VI) ions and iodide ions

    Consumption of large amounts of iodides may harm the growing foetus. Inhalation of dust may irritate respiratory tract. May act as a skin or eye irritant. May cause sensitization or allergic reaction in susceptible people. * Iodine solution, I2 Harmful through inhalation and skin contact.

  1. Investigating the Rate of the Reaction between Bromide and Bromate Ions in Acid Solution

    chemicals, further instruction is required, see below): o Chemicals in eye: Immediately wash the eye with gently-running water for at least 10 minutes. Hold back the eyelids to rinse underneath. Contact lenses must be removed. If the first aider has any concerns, send for an ambulance.

  2. Investigating how concentration affects rate of reaction

    Relating back to my theory section, this shows that the reaction, with respect to sulphuric acid, is second order. This in turn means that I have proved the final rate equation to be: Rate = k[BrO3][Br -][H+]2 This is exactly what I predicted at the beginning of my investigation.

  1. Science at Work Research . Dulux Paints, a Hospital, a leisure centre and a ...

    Health and safety: Like in the hospital the GP may have some of the same constraints to ensure safety. * Ensure all equipment is clean and safe to use * Ensure that gloves are worn when treating a patient * All needles will be put into a container * A

  2. Alkaloids are the most diverse group of secondary metabolites and over 5000 compounds are ...

    from the Canadian beaver; and muscopyridine (b) from the musk deer. Both compound have a role in communication as territorial marker substances. Insects produce a variety of structural types which include the 2,6- dialkylpiperidines of the fire ant (c), the tricyclic N-oxides of the ladybird (d) and the quinazolines of the European milliped (e).

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