Organic synthesis
Read our general notes on Risk Assessment
I am carrying out an experiment on aspirin, and in doing so I need to make acetylsalicylic acid. I am using salicylic acid and ethanoic anhydride but I was wondering how do I know how much I need of each substance and what concentration should I be using?
141108
Corrie writes .....
Concentrations (of solutions) don't enter in to it here as the reactants are used as pure substances. Salicylic acid and ethanoic anhydride react in a 1:1 ratio, so in theory you should use equal amounts (in moles) of each. However, in practice it is often the case that the cheaper reactant is added in excess, to ensure as much as possible of the more expensive reactant is used up.
In the preparation of aspirin in the Nuffield Student Chemistry Guide about 0.014 mol of salicylic acid (a solid) is used together with about 0.042 mol of ethanoic anhydride (a liquid). In addition 5 drops of 85% phosphoric acid are added to provide the acid catalyst.
You might find our tutorial on Aspirin and our list of of past question (and answers) on aspirin useful. You can find the former via the 'Practical Investigations' link on the Re:act Homepage, and the latter via the 'Sorted FAQs on Investigations' link at the bottom of the Re:act Homepage.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
Rate this page or react
Share your views on this page, 0 ratings so far
updated: 16 November 2008
