A Level Chemistry A Topic Exploration Pack – Organic Synthesis Identifying functional groups

At A Level there are many functional groups to recognise and memorise At A Level there are many functional groups to recognise and memorise. One way to deal with this large amount of information is to break it into chunks. On the following slides, the functional groups have been grouped with other similar groups. The names of the groups (like ‘simple functional groups’) are not official titles. They are just a reference for this activity, and you don’t need to learn them.

Simple functional groups Type of compound Functional group Alkene C=C Amine –NH2 Alcohol –OH Nitro compound –NO2 Haloalkane –Cl; –Br; –I Nitrile –CN Alkenes include a double bond. The other groups are attached to the carbon chain or a benzene ring.

Simple carbonyls Type of compound Functional group Aldehyde Ketone These have an oxygen atom double bonded to a carbon, which itself is bonded to only carbon and/or hydrogen.

Compound carbonyls Type of compound Functional group Carboxylic acid Acyl chloride 1° amide Cl These have an oxygen atom double bonded to a carbon, which is bonded to another atom other than carbon or oxygen.

Bridging groups Type of compound Functional group Ester 2° amide (peptide) Acid anhydride Here, a carbon is double bonded to an oxygen and bonded to another atom other than carbon or hydrogen. This atom in turn is bonded to another carbon chain.

Organic salts Functional group Diagram Carboxylate salt Phenoxide salt These have a metal ion bonded to an oxygen ion. The metal is most commonly sodium.

Aromatics / arenes These contain a benzene ring, often with alkyl groups or other functional groups attached.

Phenols These contain a benzene ring with a –OH group directly attached, often with other alkyl groups or functional groups attached.

Identifying the groups When given a complex unknown molecule it is important to be able to rule out certain groups to make identifying it easier. The following flow chart should help you to reduce the number of options down quickly. The blue boxes are key questions to help you rule certain options in or out.

Does the main chain contain anything but carbon? Is there a benzene ring? Does the main chain contain anything but carbon? Is there a –OH directly attached? Does it have a C=O bond No Phenols Aromatics Bridging groups Compound carbonyls Does the carbon have any other groups attached? Simple functional groups Yes

Tasks The worksheet contains pictures of molecules. For each molecule you need to identify all of the functional groups. For an extra challenge, have a go at naming the basic compounds. The advanced molecules are intended to have some discussion points for the group.

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