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Chemguide: Support for CIE A level Chemistry Learning outcome 16: Hydroxy compounds 16.1: Alcohols Statement 16.1.3 Statement 16.1.3(a) Find and read the statement in your copy of the syllabus. If you are working through this in order, you will already have read the page introducing alcohols. If you need to, re-read the first bit about the three types of alcohol. This statement also mentions the possibility of alcohols with more than one OH group. You have probably already come across one of these - ethane-1,2-diol, HOCH2CH2OH. If you have more than one OH group attached to a hydrocarbon chain (as long as they are on different carbon atoms), they just behave independently. Work out what each of them would do in the reactions we have looked at, temporarily ignoring the other one. | |
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Note: Out of interest only, if two OH groups end up attached to the same carbon atom, in most cases, water is lost, leaving a C=O double bond. You don't need to know that for exam purposes. | |
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Statement 16.1.3(b) Again, read the statement in your copy of the syllabus. This statement uses the effect of oxidation of the various sorts of alcohols using acidified potassium dichromate(VI) solution to help in distinguishing between primary, secondary and tertiary alcohols. You will find this covered on the page about oxidation of alcohols. You have already read the first part of this, but read the whole page again, this time concentrating on the second half about testing for the various kinds of alcohols. A problem relating this page to CIE's requirements CIE don't mention the use of Schiff's reagent either in the syllabus or in any of their questions. That means that you would have to pass the vapours in the final set of diagrams through either Tollens' reagent or Fehling's solution. Since you won't have any idea what either of those are until you have done aldehyde and ketone chemistry in more detail in Section 17, I suggest that you leave the problem for now and come back to it again after you have done Section 17. I will remind you.
© Jim Clark 2020 |
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