Obviously, the time taken for a precipitate of silver halide to appear will depend on how much of everything you use and the temperature at which the reaction is carried out. You might, for example, compare the times taken to produce a precipitate from this series of primary halogenoalkanes: You would have to keep the type of halogenoalkane (primary, secondary or tertiary) constant, but vary the halogen. Secondary halogenoalkanes do a bit of both of these.Ĭomparing the reaction rates as you change the halogen Note: If you aren't sure what primary, secondary and tertiary halogenoalkanes are, you should read the beginning of the introduction to halogenoalkanes by following this link before you go on.įor a primary halogenoalkane, the main reaction is one between the halogenoalkane and water in the solvent.Ī tertiary halogenoalkane ionises to a very small extent of its own accord. The halide ion is formed in one of two ways, depending on the type of halogenoalkane you have present - primary, secondary or tertiary. After varying lengths of time precipitates appear as halide ions (produced from reactions of the halogenoalkanes) react with the silver ions present.Īs long as you are doing everything under controlled conditions (same amounts of everything, same temperature and so on), the time taken gives a good guide to the reactivity of the halogenoalkanes - the quicker the precipitate appears, the more reactive the halogenoalkane. In this case, various halogenoalkanes are treated with a solution of silver nitrate in a mixture of ethanol and water. Note: You can read more about these tests (including an explanation of this reaction involving ammonia) by following this link to the page about testing for halide ions. Precipitate is insoluble in ammonia solution of any concentration Precipitate is almost unchanged using dilute ammonia solution, but dissolves in concentrated ammonia solution to give a colourless solution Precipitate dissolves to give a colourless solution You can sort out which precipitate you have by adding ammonia solution. It is actually quite difficult to distinguish between these colours, especially if there isn't much precipitate. Various precipitates may be formed from the reaction between the silver and halide ions: This prevents unreacted hydroxide ions reacting with the silver ions to give a confusing precipitate. The mixture is acidified by adding dilute nitric acid. The silver nitrate test is sensitive enough to detect fairly small concentrations of halide ions. There is no need to make this reaction go to completion. Use the BACK button on your browser to return to this page. Note: This reaction is described in more detail on the page about reactions of halogenoalkanes with hydroxide ions. The halogen atom is displaced as a halide ion: Everything will dissolve in this mixture and so you can get a good reaction. The halogenoalkane is warmed with some sodium hydroxide solution in a mixture of ethanol and water. The most effective way is to do a substitution reaction which turns the halogen into a halide ion, and then to test for that ion with silver nitrate solution. Silver nitrate solution can be used to find out which halogen is present in a suspected halogenoalkane. This page looks at how silver nitrate solution can be used as part of a test for halogenoalkanes (haloalkanes or alkyl halides), and also as a means of measuring their relative reactivities. REACTIONS INVOLVING HALOGENOALKANES AND SILVER NITRATE SOLUTION This implies that bromine is not a better oxidizing agent than chlorine or, in other words, that chlorine is a better oxidizing agent than bromine.Halogenoalkanes (haloalkanes) and silver nitrate There will be no color change the hexane layer will remain orange.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |