MediumChemistryHigh School (11–12)Organic Compounds with Functional Groups › Aldehydes, Ketones and Carboxylic AcidsNumerical

Propanone (58.08 g/mol) is converted to its oxime (73.09 g/mol) with hydroxylamine, and to its…

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Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

Propanone ( $58.08\ \text{g/mol}$ ) is converted to its oxime ( $73.09\ \text{g/mol}$ ) with hydroxylamine, and to its 2,4-dinitrophenylhydrazone ( $238.20\ \text{g/mol}$ ) with 2,4-dinitrophenylhydrazine. In each case one mole of propanone gives one mole of product. Find the amount of propanone in $0.580\ \text{g}$ and the mass of the 2,4-DNP derivative it can give. Then find the mass of oxime from $2.90\ \text{g}$ of propanone. Name the small molecule that is lost in both reactions.

Need a reminder? The key ideaShow

A nucleophile attacks the carbonyl carbon, the carbon changes from $sp^2$ to $sp^3$ , and the oxygen then takes a proton. Alkyl groups lower the positive charge and crowd the carbon, so methanal > other aldehydes > ketones. HCN gives a cyanohydrin, NaHSO $_3$ a bisulphite compound, alcohols with dry HCl an acetal, and $\text{H}_2\text{N-Z}$ compounds a C=N compound and water.

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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← Ethanal (44.05 g/mol) reacts with HCN, in a trace of base, to give a cyanohydrin…4.40 g of ethanal (44.05 g/mol) is warmed with an excess of methanol (32.04 g/mol) and a little dry… →

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