an aldehyde a carboxylic acid

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1 An Introduction to Functional Groups in rganic hemistry What are Functional Groups Functional groups are common bonding patterns found in organic molecules Examples 3 an aldehyde 3 a carboxylic acid eactivity of Functional Groups eactivity of Functional Groups 2 Li Li Tollen's eagent + silver mirror a a K K Tollen's eagent silver mirror 1

2 eactivity of Functional Groups Functional Groups ontaining arbon and ydrogen nly + Tollen's eagent + Tollen's eagent 2 no silver mirror produced + Tollen's eagent??? + silver mirror Alkanes contain only sp 3 hybridized carbon atoms, and therefore possess only single bonds. A compound is only called an alkane if it contains none of the other functional groups. Alkenes contain at least one carbon-carbon double bond. Alkynes contain at least one carbon-carbon triple bond. yclic ydrocarbons an alkane 3 3 an alkene 3 an alkyne An alkane which contains a ring made up of three or more atoms is called a cycloalkane. Likewise, a cycloalkene contains a carbon-carbon double bond somewhere in a ring of carbon atoms. ycloalkynes are relatively rare, for reasons we will see later (think bond angles). We will not consider these as distinct functional groups We still classify a cycloalkene as an alkene a cycloalkane a cycloalkene 2

3 Aromatics Alkyl alides The term aromatic has a rather detailed meaning which we will discuss next semester. For now, when we describe a compound as containing an aromatic group, we mean to say that it contains a benzene ring. Three equivalent ways of representing the benzene molecule ote that the benzene ring is not considered either an alkene or a cycloalkene; the special term aromatic makes the presence of the ring and double bonds understood. As we shall see, aromatic compounds react in distinctly different ways than do alkenes, owing to delocalization of electrons within the ring. Alkyl halides are compounds which have a halogen atom bonded to a carbon atom somewhere in the molecule. We are sometimes more specific, calling a compound an alkyl chloride, alkyl bromide, etc. 3 l 3 Br Alcohols ompounds which contain the hydroxyl group - bonded to carbon ( ) make up the class of compounds called alcohols. Technically, the carbon should be sp 3 hybridized. 3 3 Thiols and Amines Thiols are similar to alcohols in structure, with a sulfur atom replacing the oxygen atom: S Amines have a nitrogen atom bonded to at least one carbon atom; the remainder of its bonds may be to carbon or hydrogen. 3

4 Thiols and Amines Ethers 3 3 S 3 3 S alcohols thiols The ether functional group is described as an sp 3 oxygen atom bonded to two carbon atoms, and may be symbolized as --'. and ' may be the same groups or different amines arbonyl-ontaining Functional Groups A carbonyl group is made up of a carbon atom double bonded to an oxygen atom. The carbon atom is not bonded to any other heteroatom. the carbonyl group We will not consider the carbonyl group to be a functional group in-and-of itself; rather, it is the essential portion of two functional groups: aldehydes and ketones. Ketones The ketone functional group contains a carbonyl group, with the carbon of that group bonded to two other carbon atoms. and ' may or may not be the same. ' a ketone 4

5 Aldehydes The aldehyde functional group contains a carbonyl group, with the carbon of that group bonded to at least one hydrogen atom. The other bond is either to a carbon atom or another hydrogen atom. is an alkyl group or another hydrogen atom in the case of formaldehyde. an aldehyde arboxylic Acids A carboxyl group looks similar to a carbonyl group, but at least one of its sigma bonds is to a second oxygen atom. the carboxyl group The carboxylic acid functional group has a hydrogen atom bonded to this oxygen atom. It is generally acidic, for reasons we discussed in hapter ne. The other bond need not be specified; it may be an alkyl group, a hydrogen atom, or another. carboxylic acid arboxylic Acid Derivatives There are several functional groups which are structurally similar to carboxylic acids. The ester functional group has an alkyl group in place of the hydrogen bonded to the carboxylic oxygen atom. an ester ' arboxylic Acid Derivatives The anhydride functional group is a two-sided carboxyl group: and ' may or may not be the same. an anhydride ' and ' may or may not be the same. 5

6 arboxylic Acid Derivatives The acid chloride (or acyl chloride) functional group has a chlorine atom in place of the carboxylic oxygen l an acid chloride arboxylic Acid Derivatives An amide has an sp 3 hybridized nitrogen atom in place of the carboxylic oxygen atom. The nitrogen atom is bonded to 0-2 alkyl groups. The remaining bonds are to hydrogen. Do not confuse amides with amines! an amide Practice ircle and label all the functional groups in the molecules below. 3 2 Practice Solutions ether 3 alcohol 2 ketone 3 l 3 3 ester 3 l 3 3 alkyl halide alkene alkyne aldehyde F S 3 3 ether F alkyl halide S thiol 3 3 amine 6