Question!What do you know about alcohols?

Alcohols and Alkanoic acids

Organic Chemistry

Objectives

03

01

02Alkanoic acids

-identify alkanoic acids by their functional groups

Properties of Alcohols and Alkanoic acids

- relate the properties of alcohols, acids and to their functional groups

Alcohols- identify alcohols by their functional groups

AlcoholsAnd their properties

01

Alcohols❖ Alcohols are a homologous series with the general formula

Cn H2n+1 OH

❖ They have the hydroxyl group , -OH, as their functional group

❖ The strength of the reactions decreases as the number of

carbon atoms per molecules

Properties of Alcohols❖ They are colourless and sweet- smelling

❖ Alcohols are polar because they possess the polar -OH group

❖ They are less volatile than corresponding alkanes due to the -OH

group ,the forces of attraction between alcohol molecules are

stronger than the forces between non-polar alkane molecules

with the same number of carbon atoms

Properties of Alcohols

❖ All alcohols are liquids or solids at room temperature.

❖ Their boiling points increase as the number of carbon atoms per

molecule increases.

❖ Alcohols are soluble in water because water is a polar solvent. Their

solubility decreases as the number of carbon atoms per molecule

increases.

Alkanoic acidsStuff about them02

Alkanoic acids (CnH2n+1COOH)

❖ Alkanoic acids (or carboxylic acids) have the carboxyl group ( -COOH)

❖ Alkanoic acid molecules are polar due to the -OH part of the functional

group being polar.

❖ Alkanoic acids are less volatile than their corresponding alkanes and are

soluble in water. When they dissolve in water they partially ionise, and are

therefore weak acids

Ethanoic acid in water

Structure of Alkanoic Acids

Properties of Alkanoic acids❖ The alkanoic acids are colourless and have a vinegary smell.

❖ An alkanoic acid is less volatile than an alcohol or ester of similar

mass because of the polar carboxyl (-COOH) group.

❖ Due to the polar -OH group, the alkanoic acids are soluble in

water. However, the solubility decreases as the hydrocarbon

chain increases.

Reactions of Ethanol03

Reactions of Alcohols❖ Ethanol burns easily in air or oxygen

Ethanol burns in air or oxygen to produce carbon dioxide and

water as steam. It burns with a clear, blue, non-smoky flame

because of the low ratio of carbon to hydrogen atoms in the

molecules. The reaction is exothermic:

Combustion of Ethanol

Reactions of Ethanol❖ Ethanol reacts with reactive metals like sodium

Ethanol reacts with sodium to form sodium ethoxide (C2H5ONa)

and hydrogen:

Reaction with Sodium

Reactions of Ethanol❖ Ethanol undergoes dehydration

Ethanol can be dehydrated to ethene in two ways:

1. Heating ethanol at a temperature of about 170 °C with excess concentrated

sulfuric acid. The acid acts as a catalyst (showcased next slide)

2. Passing ethanol vapour over heated aluminium oxide. The aluminium oxide

acts as a catalyst.

Dehydration of Ethanol

Reactions of Ethanol❖ Ethanol undergoes oxidation

Ethanol is oxidised to ethanoic acid when heated with acidified

potassium manganate(VII) solution or acidified potassium dichromate

(VI) solution. Ethanol acts as a reducing agent.

Oxidation of Ethanol

Reactions of Ethanol❖ Ethanol undergoes oxidation

Orange acidified potassium dichromate (VI) crystals can be used in the

breathalyser test to determine the alcohol content of a driver's breath.

The driver blows over the crystals and if ethanol vapour is present, it

reduces the orange dichromate(VI) ion (Cr₂O₂²-) to the green

chromium(III) ion (Cr³+). This turns the crystals green.

Reactions of Ethanol❖ Ethanol reacts alkanoic acids

Ethanol reacts with alkanoic acids to produced an ester

and water

Production of Ethanol04

Production of Ethanol❖ Production through Fermentation of Carbohydrates

Ethanol can be produced by using yeast to ferment carbohydrates under

anaerobic conditions (without oxygen). Yeast produces enzymes that

break down complex carbohydrates into simple sugars, mainly glucose. It

then produces the enzyme zymase which changes the simple sugars into

ethanol and carbon dioxide:

Fermentation of Glucose

Production of EthanolFermentation stops when the concentration of ethanol in the

fermentation mixture reaches about 14%. At this concentration, the

ethanol starts to denature the zymase and this stops it from working.

Ethanol which is about 96% pure is then obtained from the fermentation

mixture using fractional distillation, collecting the fraction that distils at

78 °C.

Production of Ethanol

Fractional distillation of Ethanol

Production of EthanolFermentation of carbohydrates is used to produce a variety of different

alcoholic beverages, including wine and rum.

● Wine is mainly made from grapes in a winery. The yeast is added to

the crushed grapes and it ferments the sugars present. Air should

not come into contact with the wine because certain aerobic

bacteria oxidise the ethanol to ethanoic acid, or vinegar, causing the

wine to become sour:

Oxidation of Ethanol ( by bacteria)

Production of Ethanol

● Rum is made from molasses in a rum distillery. The yeast is added to

the molasses and it ferments the sugars present. The mixture is then

fractionally distilled. The distillate is diluted with water and

transferred to oak barrels to be aged.

Reactions of Ethanoic Acid05

Reactions of Ethanoic AcidAqueous solutions of alkanoic acids react in a similar way to inorganic

acids, such as hydrochloric acid, though the reactions are slower

because the acids are weak. The hydrogen in the functional group can be

replaced directly or indirectly by a metal to form a salt. The salts formed

by ethanoic acid are called ethanoates.

Reactions of Ethanoic acid❖ Aqueous ethanoic acid reacts with reactive metals

Ethanoic acid reacts with reactive metals to form a salt and hydrogen

gas:

Reactions of Ethanoic acid❖ Aqueous ethanoic acid reacts with metal oxides and metal hydroxides

Ethanoic acid reacts with metal oxides and hydroxides to form a salt and

water:

Reactions of Ethanoic acid❖ Aqueous ethanoic acid reacts with metal carbonates

Ethanoic acid reacts with metal carbonates to form a salt, carbon

dioxide and water.

Reactions of Ethanoic Acid

Anhydrous (water-free) ethanoic acid reacts with alcohols to produce an

ester and water