What are Functional Groups

An Introduction to Functional „ Functional groups are common bonding Groups in Organic Chemistry patterns found in organic molecules „ Examples

O O

C C

H CH3 HO CH3 an aldehyde a carboxylic acid

Reactivity of Functional Groups Reactivity of Functional Groups

O O + Tollen's Reagent + silver mirror 2 Li + 2 H2O → 2 LiOH + H2 C C H CH3 HO CH3 2 Na + 2 H2O → 2 NaOH + H2 O O + silver mirror 2 K + 2 H2O → 2 KOH + H2 C + Tollen's Reagent C H CH2CH3 HO CH2CH3

1 Functional Groups Containing Reactivity of Functional Groups Carbon and Hydrogen Only

O O 3 „ Alkanes contain only sp hybridized carbon

C + Tollen's Reagent C + silver mirror atoms, and therefore possess only single H R HO R bonds. O „ A compound is only called an alkane if it contains + Tollen's Reagent no silver mirror none of the other functional groups. C produced HO R „ Alkenes contain at least one carbon-carbon double bond. O CH O 2 „ Alkynes contain at least one carbon-carbon C C + Tollen's Reagent ??? triple bond. H OH

Cyclic Hydrocarbons

„ An alkane which contains a ring made up of three CH CH or more atoms is called a cycloalkane. 2 3 CH3 H CC „ Likewise, a cycloalkene contains a carbon-carbon CH3 C CH3 H CCCH3 double bond somewhere in a ring of carbon atoms. H CH3 CH3 „ Cycloalkynes are relatively rare, for reasons we will see later (think bond angles). an alkane an alkene an alkyne „ We will not consider these as distinct functional groups „ We still classify a cycloalkene as an alkene

a cycloalkane a cycloalkene

2 Aromatics Alkyl Halides

„ The term aromatic has a rather detailed meaning which we will discuss next semester. „ Alkyl halides are compounds which have „ For now, when we describe a compound as containing an a halogen atom bonded to a carbon aromatic group, we mean to say that it contains a benzene ring. atom somewhere in the molecule.

„ We are sometimes more specific, calling a compound an alkyl chloride, alkyl Three equivalent ways of representing the benzene molecule bromide, etc.

„ Note that the benzene ring is not considered either an alkene or a cycloalkene; the special term aromatic makes the H H presence of the ring and double bonds understood. H C Cl H C Br „ As we shall see, aromatic compounds react in distinctly different ways than do alkenes, owing to delocalization of electrons within the ring. CH3 CH3

Alcohols Thiols and Amines

„ Compounds which contain the hydroxyl „ Thiols are similar to alcohols in group -OH bonded to carbon (R–OH) structure, with a sulfur atom replacing make up the class of compounds called the oxygen atom: R–SH alcohols. 3 „ Amines have a nitrogen atom bonded to „ Technically, the carbon should be sp hybridized. at least one carbon atom; the H OH remainder of its bonds may be to carbon or hydrogen. H3CCCH3

OH

3 Thiols and Amines Ethers

H OH alcohols H3CCCH3 „ The ether functional group is described as 3 OH an sp oxygen atom bonded to two carbon atoms, and may be symbolized as R-O-R'. H SH thiols „ R and R' may be the same groups or H CCCH 3 3 different. SH

CH3 CH3 H N amines CH3 O C CH3 H3CCCH3 CH3 CH3CH2 O CH2CH3 O NH2 CH3

Carbonyl-Containing Functional Groups Ketones

„ „ A carbonyl group is made up of a carbon atom The ketone functional group contains a carbonyl double bonded to an oxygen atom. The carbon group, with the carbon of that group bonded to atom is not bonded to any other heteroatom. two other carbon atoms. O „ R and R' may or may not be the same.

C O

the carbonyl group C R R' „ We will not consider the carbonyl group to be a functional group in-and-of itself; rather, it is the a ketone essential portion of two functional groups: aldehydes and ketones.

4 Aldehydes Carboxylic Acids

„ The aldehyde functional group contains a „ A carboxyl group looks similar to a carbonyl group, but at carbonyl group, with the carbon of that group least one of its sigma bonds is to a second oxygen atom. O bonded to at least one hydrogen atom. The O C C other bond is either to a carbon atom or another O OH

hydrogen atom. the carboxyl group carboxylic acid „ R is an alkyl group or another hydrogen atom in „ The carboxylic acid functional group has a hydrogen atom the case of formaldehyde. bonded to this oxygen atom. It is generally acidic, for O reasons we discussed in Chapter One.

„ The other bond need not be specified; it may be an alkyl C R H group, a hydrogen atom, or another –OH. an aldehyde

Carboxylic Acid Derivatives Carboxylic Acid Derivatives

„ There are several functional groups which are „ The anhydride functional group is a two-sided structurally similar to carboxylic acids. carboxyl group: O O „ The ester functional group has an alkyl group in

place of the hydrogen bonded to the carboxylic C C oxygen atom. O R O R'

C an anhydride R OR'

an ester „ R and R' may or may not be the same.

„ R and R' may or may not be the same.

5 Carboxylic Acid Derivatives Carboxylic Acid Derivatives

3 „ An amide has an sp hybridized nitrogen atom in „ The acid chloride (or acyl chloride) functional place of the carboxylic oxygen atom. group has a chlorine atom in place of the O carboxylic oxygen O C R N C R Cl an amide

an acid chloride „ The nitrogen atom is bonded to 0-2 alkyl groups.

„ The remaining bonds are to hydrogen.

„ Do not confuse amides with amines!

Practice Practice—Solutions

Circle and label all the functional groups in the molecules below. ether ketone OH CH3 OH CH3 O alcohol O

CH2 CH O C C CH2 CH O C C

CH3 CH3 Cl CH3 ester Cl CH3 aldehyde O O O O alkyl halide H H alkene

O CH3 O CH3 alkyne

C CH C CH

O N O N CH thiol CH SH 3 ether SH 3 H3C H3C alkyl halide amine F F

6