November 26, 2015

Homework Help: Melting point

Posted by Sheryl on Tuesday, September 26, 2006 at 6:37pm.

Could you tell me what the melting point for a crystallized sulfanamide is? Also, we will have to determine the m.p. of an impure sulfanamide. Any idea of a temperature range for that? Will it be higher of lower? Probably hard to tell since I don't know what the impurity will be. The lab for crystallization is tomorrow.

Thanks from Sheryl

I was unable to find any reference to sulfanamide in The Merck Index. Is that a class of compounds or is it the name of a distinct compound. As for the melting point, don't you think the melting point of an impure sample will be less than that of the pure sample? (Remember the molal freezing point constants??) And the range may be of the order of 2-5 degrees

Looks like I misspelled it. It is sulfanilamide. Any better luck with that one? It is a sulfa drug.


Of course. Even I, of no organic fame, recognize sulfanilamide. mp, according to The Merck Index, is 164.5-166.5 and pKa = 10.43. That tells you the high side of an impure product. Impurities will reduce the melting point because of the molal freezing point behavior.

Just for the fun of it I went to and typed in "melting point sulfanilamide" without the quotation marks. I obtained 16,300 hits and the first four gave values ranging from 165 to 167.

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