[tracy]

If I had two bottles of which the labels had fallen off and the possibilities for each of the bottles was methyl-3-nitrobenzoate and triphenylphosphine; how would I tell which one is which? They both have more or less the same melting point and no distinct smells or colour differences. Could I react methyl bromide with one of the two? If it reacts with triphenylphosphine, it would release bromide ions into the solution and cause the colour to change reddish-brown (to my understanding). If the methyl bromide reacted with the methyl-3-nitrobenoate - no visible change would take place, right?

[madscientist]

methyl-3-nitrobenzoate:

Mr = 181.1476  

melt. point = 78  

Boil. point = 279  


triphenyl phosphine:

Mr = 262.29026  

Melt. point = 80  

Boil. point = 377

See if its safe to boil the two and measure their boiling points, or weigh out samples of the two and compare.

I could be totally wrong with this cause im only a second year student but any response is better than no response i guess.

Hope this helps,

madscientist :albert:

[Pelle]

Are bromide ions brown-reddish in solution?

Look the Wittig-reaction up. Methyl-3-nitrobenzoate is an ester and has a nitro-group, right? Do those groups react with primary alkyl halides? Does anyone of your two compunds react with sodium hydroxide?

Assume you take two small samples of each compund and put them in a small container with some water in it, then try the compunds with methyl iodide (BTW, this one is pretty nasty and gaseous, right?) and sodium hydroxide. What products form and are starting materials or products soluble in water?

[tracy]

Apparently the correct answer is to do with shared melting points. It's pretty simple, actually. I should get a pure sample of methyl-3-nitrobenzoate. If i mix a little of the one unknown with the pure and find the melting point and it is exactly the same as that of methyl-3-nitrobenzoate; then the sample I mixed with the pure is nitrobenzoate. If I mix the other unknown (triphenylphosphine) with the pure (and known) methyl-3-nitrobenzoate, I will find a depression in the melting point as a result of impurity, i.e. a melting point below 79 degrees. Thus this other unknown is then the triphenylphosphine.
Thanks for the help all of you. (And I am also only a second year).