FUNCTIONAL GROUPS · PHYSICAL PROPERTIES The hydroxyl group is polar and allows for hydrogen...

FUNCTIONAL GROUPSSCH4U7 - Organic Chemistry

Monday, January 30, 2012

FUNCTIONAL GROUPS

Functional groups are groups of atoms other than carbon and hydrogen linked to a hydrocarbon

They are where the real chemistry happens

They also give a compound distinct properties, like melting points, boiling points and reactivity

R is often used to represent a chain of hydrocarbons instead of writing them all out


A PREVIEW!


ALCOHOLS

Alcohols contain a hydroxyl (OH) group connected to carbon #1

General formula is R - OH where R is a hydrocarbon

Suffix is “ol”

Prefixes remain the same

Name these!

Methanol Pentan-1-olMonday, January 30, 2012

CLASSIFYING ALCOHOLSAlcohols are classified according to how many carbons the first carbon is attached to.

1) Primary alcohol-one in which the carbon to which the OH group is attached is attached to only ONE other C atom.

2) Secondary alcohol-one in which the carbon to which the OH group is attached is attached to only TWO other C atoms.

3) Tertiary alcohol-one in which the carbon to which the OH group is attached is attached to only THREE other C atoms.


SPECIAL ALCOHOLS

If there are 2 hydroxyl groups present then use the suffix “diol”

Draw out this compound: CH2OHCH2OH

Name it

If there are 3 hydroxyl groups present then use the suffix “triol”

Draw out this alcohol: CH2OHCHOHCH2OH

Ethanediol

propanetriol


PHYSICAL PROPERTIES

✴ The hydroxyl group is polar and allows for hydrogen bonding

✴Due to the increased intermolecular forces, the melting and boiling points of alcohols are higher than the corresponding hydrocarbon. MP & BP increases with chain length

✴ Since the hydroxyl group allows for hydrogen bonding, alcohols are quite soluble in water

✴ As the hydrocarbon chain increases in length, the solubility in water decreases. Why?

✴ C1-C5= highly soluble; C5-C7= moderately soluble; C8and above = slightly soluble/insoluble


TRY IT !

Name these alcohols:

Draw these alcohols:

5-ethyl-3-methyl-2,3-nonanediol

3,4-dimethylhexan-2-ol


TRY IT !


ALKYL HALIDES

R - X (where X is any halogen: F, I, Br, Cl)

Prefix used: fluoro, iodo, bromo, chloro

Use numbers to indicate where the halogen is

Same classification as with alcohols (primary, secondary, tertiary)


PHYSICAL PROPERTIESAs we have seen before, the boiling point increases the longer the chain

Solubility DEcreases the longer the chain, since it is more hydrophobic

Name these haloalkanes:


CARBONYL GROUPSCarbonyl group is C=O

There are 2 classes of organic compounds which contain this:

Aldehydes - contain C=O at the END of a chain

Ketones - contain C=O in the middle of a chain


ALDEHYDESSuffix: “al”

Carbon which is bonded to oxygen MUST be counted as number 1. Always. No exceptions. This means no number is needed to indicate where the oxygen is.

In the condensed form, abbreviated at CHO (avoiding confusion with alcohols)

ie) Ethanal

Draw & name: C2H5CHO

Draw: 4-methylpentanalMonday, January 30, 2012

KETONES

Suffix: “one”

Carbon which is bonded to oxygen MUST be indicated by a number

In the condensed form, abbreviated at CO.

ie) Propanone - why no number?

Draw & name: C3H7COCH3

Draw: Hexan-3-one


PHYSICAL PROPERTIES

C=O is a polar group and creates a dipole

The intermolecular forces are stronger than in corresponding alkanes, but lower than in alcohols (since alcohols have hydrogen bonding)


CARBOXYLIC ACIDA carboxylic acid is an organic acid which contains the functional group

Suffix used “oic acid”

Abbreviated COOH

Numbers are not required because the first carbon MUST be the one bonded to the oxygen and hydroxyl group


NEAT-O!

Draw & name: C2H5COOH

Draw: 3,4-dichloro-2,3-dihydroxyhexanoic acid!

Name:


PHYSICAL PROPERTIES

Since they contain both C=O and OH, they can form strong hydrogen bonds

Carboxylic acids will have the highest melting point of all comparable organic compounds

1) Order the following in ascending order of boiling point: Propanal, propanol, propanoic acid, propane

2) Does 3-pentanoic acid exist? If yes, draw it. If no, explain why.


OTHER FUNCTIONAL GROUPS

At the SL level, you are only required to recognize the following groups:

Esters:

Amines:

Amides:

Ethers:

Benzene (phenyl)


TRY IT!


FUNCTIONAL GROUPS · PHYSICAL PROPERTIES The hydroxyl group is polar and allows for hydrogen...

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