AlcoholsOh yeah!

Alcohol• Compound where a hydroxyl group (-OH) replaces one of the hydrogens

on a carbon• General Formula:

– R- OH• Example:

– CH3CH2CH2OH– 1-propanol

Alcohol Nomenclature• Alcohols end with the suffix “-ol”• Like alkenes and alkynes, the longest continuous chain must contain the

hydroxyl group (-OH).– Also, count the carbons so that the hydroxyl group has the lowest

number possible• Unlike alkenes/alkynes, the location of the hydroxyl group interrupts the

base name and the number goes directly before the –ol• Branches are names as usual• Example:

• 3-methylbutan-1-ol

Types of Alcohols• Each alcohol is defined by having a C-OH bond. So there are three other

bonds on that carbon… to determine what type of alcohol it is, simple count the things bonded to the carbon that aren’t hydrogens. (often labeled as “R” groups)

• 3 Types– Primary Alcohol

• Alcohol with only 1 “R” group….– Secondary Alcohol

• Alcohol with 2 “R” groups…– Tertiary Alcohol

• Alcohol with 3“R” groups…

Properties of Alcohols• Hydroxyl group is polar and allows for hydrogen bonding to water

molecules– Alcohols have high melting and boiling points than corresponding

alkanes– Alcohols with fewer than 7 carbons are liquids are room temp

• Methanol and ethanol are colourless, have low boiling points, and are liquids with slightly sharp, sweet smells

– Alcohols with less than 5 carbons dissolve both in water and in non-polar organic liquids

• Longer carbon chain alcohols become progressively less soluble in water

***Reactions of Alkenes and Alkynes

• Oxidation– Alkenes undergo an oxidation reaction with

acidified potassium permanganate, KMnO4/H+ (not simply KMnO4)

• Forms a “diol”

Reactions of Alcohols• Oxidation Reactions• Alcohols can undergo oxidation reactions with acidified potassium

permanganate, KMnO4/H+ or acidified potassium dichromate K2Cr2O7/H+

– Oxidation of Primary Alcohols• Symbol [O] above a rxn arrow indicates an oxidation rxn.• 1st product of an oxidation of primary alcohol is and aldehyde.

Aldehydes can then be oxidized into carboxylic acids

Reaction of Alcohols• Test for Primary Alcohol

– Tollen’s Test:• Reduces Ag+ to solid Ag – seen as a black suspension or ‘silver

mirror’– happens with Aldehydes (the 1st product of oxidation of

primary alcohols). Secondary alcohols don’t create aldehydes – they create ketones. Ergo, Tollen’s test can be used to tell the difference b/w aldehydes and ketones

Reaction of Alcohols• Test for Primary Alcohol

– Fehling’s or Benedict’s Reagents:• Uses copper compounds to test for aldehyde• Cu2+ (blue) is reduced by aldehydes to Cu+ (red suspension)

Reaction of Alcohols• Reflux Equipment is used to completely oxidize primary alcohols to

carboxylic acids (returns vaporized aldehydes to mixture to finish oxidizing)

Reaction of Alcohols• Oxidation Reactions

– Oxidation of Secondary Alcohols• Oxidised to a ketone (RCOR’)

– Oxidation of Tertiary Alcohols– Can’t happen

Reaction of Alcohols• Substitution with Thionyl Chloride (SOCl2)

– Alcohols react with chlorinating agents to give a choloralkane

Reaction of Alcohols• Condensation reaction (Esterification)

– Alcohol + Carboxylic Acid ester (RCOOR’)• Often have sweet, fruity smell

– Usually done with dehydrating agent (concentrated sulfuric acid)– Uses reflux equipment – no loss to evaporation

Reaction of Alcohols• Elimination Reaction of Alcohols

• Reverse of Markovnikov’s Rule: H is eliminated from the carbon atom which has the lowest number of H atoms