CONVERTING CARBOXYLIC ACIDS INTO ACYL CHLORIDES (ACID CHLORIDES)

This page looks at ways of swapping the -OH group in the -COOH group of a carboxylic acid for a chlorine atom. This produces useful compounds called acyl chlorides (acid chlorides). It covers the use of phosphorus(V) chloride and phosphorus(III) chloride as well as sulphur dichloride oxide (thionyl chloride). Replacing -OH by -Cl Introduction We are going to be looking at converting a carboxylic acid, RCOOH, into an acyl chloride, RCOCl. Acyl chlorides are also known as acid chlorides. By far the most commonly used example of the conversion of a carboxylic acid into an acyl chloride is ethanoic acid to ethanoyl chloride. Acyl chlorides are very reactive, and can be used to make a wide range of other things. That's why they are important.
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Replacing the -OH group using phosphorus(V) chloride, PCl₅ Phosphorus(V) chloride is a solid which reacts with carboxylic acids in the cold to give steamy acidic fumes of hydrogen chloride. It leaves a liquid mixture of the acyl chloride and a phosphorus compound, phosphorus trichloride oxide (phosphorus oxychloride) - POCl₃. The acyl chloride can be separated by fractional distillation. For example: Replacing the -OH group using phosphorus(III) chloride, PCl₃ Phosphorus(III) chloride is a liquid at room temperature. Its reaction with a carboxylic acid is less dramatic than that of phosphorus(V) chloride because there is no hydrogen chloride produced. You end up with a mixture of the acyl chloride and phosphoric(III) acid (old names: phosphorous acid or orthophosphorous acid), H₃PO₃. For example: Again, the ethanoyl chloride can be separated by fractional distillation. Replacing the -OH group using sulphur dichloride oxide (thionyl chloride) Sulphur dichloride oxide (thionyl chloride) is a liquid at room temperature and has the formula SOCl₂. Traditionally, the formula is written as shown, despite the fact that the modern name writes the chlorine before the oxygen (alphabetical order). The sulphur dichloride oxide reacts with carboxylic acids to produce an acyl chloride, and sulphur dioxide and hydrogen chloride gases are given off. For example: The separation is simplified to an extent because the by-products are both gases. You would obviously still have to fractionally distil the mixture to separate the acyl chloride from any excess acid or sulphur dichloride oxide.

PROPERTIES OF THE PERIOD 3 CHLORIDES

This page looks at the structures of the chlorides of the Period 3 elements (sodium to sulphur), their physical properties and their reactions with water. Chlorine and argon are omitted - chlorine because it is meaningless to talk about "chlorine chloride", and argon because it doesn't form a chloride. A quick summary of the trends The chlorides The chlorides we'll be looking at are: NaCl MgCl 2 AlCl 3 SiCl 4 PCl 5 S 2 Cl 2 PCl 3 There are three chlorides of sulphur, but the only one mentioned by any of the UK-based syllabuses (A level or its equivalents) is S 2 Cl 2 . As you will see later, aluminium chloride exists in some circumstances as a dimer, Al 2 Cl 6 . The structures Sodium chloride and magnesium chloride are ionic and consist of giant ionic lattices at room temperature Aluminium...

ADDITION-ELIMINATION REACTIONS OF ALDEHYDES AND KETONES

Which gives addition reaction with aldehyde and ketone? What is addition-elimination reaction with example? Which reaction is a condensation or addition-elimination reaction? What is the mechanism involved in the reaction of aldehydes and ketones with 2 4 DNP?

FRACTIONAL DISTILLATION OF IDEAL MIXTURES OF LIQUIDS

This page explains how the fractional distillation (both in the lab and industrially) of an ideal mixture of liquids relates to their phase diagram. This is the second page in a sequence of three pages. Important: If you have come straight to this page from a search engine and are looking for simple factual information about fractional distillation, this is probably not the page for you! It deals with the theory behind fractional distillation. Again, if you have come straight to this page, you won't make much sense of it unless you first read the page about phase diagrams for ideal mixtures . You will find a link at the bottom of that page which will bring you back here again. Using the phase diagram On the last page, we looked at how the phase diagram for an ideal mixture of two liquids was built up. I want to start by looking again at material from the last part of that page. The next diag...

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