alcohols esters and carboxylic acids 2

8/2/2019 Alcohols Esters and Carboxylic Acids 2

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1

Teacher: Mr. J. Graham

Students: Stuart McKenzie

Jhenelle HewTalia Dubrisingh

Class: 5B

Date:



Organic Chemistry



3

Table of Contents

Introduction 4

Alcohols 5

Carboxylic Acids 9

Esters 13Ethanol 16

Quiz 25

References 31



4

Introduction

The main objective of this presentation was to do independent researchand learn about organic chemistry. The group was given Option 6.The topics focused on in this question were alcohols, acids andesters and every member contributed towards making this powerpoint presentation a success.

The first part of the question said to identify alcohols, acids and estersby their functional groups, and this was done by Stuart McKenzie.The second part was done by Talia Dubrisingh and it relates theproperties of alcohols, acids and esters to their functional groups.Talia also organised the information for the project into apresentable format. The last part describing the reactions of ethanol,

including equations and necessary conditions was done by JhenelleHew. Jhenelle also wrote the introduction for the project. Eachmember contributed to the quiz and the reference section.



5

Alcohols



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Alcohols

Alcohols in chemistry refer to organiccompounds in which a hydroxyl group isbound to a carbon atom of an alkyl group.

The general formula is CnH2n+1OH.

The hydroxyl (-OH) group is the

functional group.



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Properties of Alcohols:

Alcohols are soluble in water. This isespecially true for smaller compounds.

They have higher melting and boilingpoints than their corresponding alkanes.

Alcohols are good solvents.

They evaporate quickly in comparisonwith water.



8

Properties of Alcohols Continued:

Alcohols combust in air to produce carbondioxide, water vapour and heat. This allows theuse of alcohols as fuels. e.g. methanol, ethanol

e.g. CH3OH (l) + 3/2 O2(g) CO2(g) + 2H2O(l) +

heatAlcohols react with reactive metals to produce

hydrogen gas and salts called alkoxides.e.g. 2Na(s) + 2CH3CH2ONa(s) + H2(g)

Alcohols can be converted to esters by reactingthem with strong oxidising agents or through acondensation reaction, using organic acids andsulphuric acid.



9

CarboxylicAcids



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Carboxylic Acids

An acid in organic chemistry is acompound with acidic properties.

The general formula is CnH2n+1COOH

The most common ones are carboxylicacids, whose acidity is associated withtheir (functional) carboxyl group: -COOH.



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Properties of Carboxylic Acids:

These acids are soluble in water.

They have relatively high melting and boilingpoints.

They are not as reactive as their correspondingalcohols.

Carboxylic acids react with metals to form a salt

and hydrogen gas.e.g. Mg (s) + 2CH3COOH (aq) (CH3CO2)2Mg (aq)

+ H2 (g) [Magnesium ethanoate]



12

Properties of Carboxylic Acids continued:

They react with metal oxides and hydroxides toproduce salt and water (neutralisation reaction).

e.g. 2CH3COOH(aq) + CuO(s) (CH3COO)2Cu(aq) + H2O(l)

These acids produce carbon dioxide, salt andwater when reacted with carbonates andhydogencarbonates.

e.g. 2CH3COOH (aq) + Na2CO3 (aq) 2CH3COONa

(aq) + H2O (l) + CO2 (g) They react with alcohols in an esterification

reaction to form esters.



13

Esters



15

Properties of Esters

Esters have low melting and boilingpoints.

Short chain esters are aromatic.

They are soluble in alcohols.

Esters of long chain acids are found in

vegetable oils and animal fats.



16

Ethanol



17

Ethanol: The Manufacture of Ethanol

There are two processes commercially used to manufactureethanol. These are:

Hydration of ethene

Fermentation of carbohydrates

The hydration of ethene is an industrial process. Water isadded to ethene by passing a mixture of steam andethene over a catalyst of phosphoric acid in silica gel at

300°C and 60 atmospheres.The product of the mixture is condensed and fractionallydistilled to give roughly 95% pure ethanol.



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The Manufacture of Ethanol Continued

The fermentation of carbohydrates is the partialbreakdown of glucose by anaerobic respiration whereethanol, carbon dioxide and energy are products.

This is done by using a carbohydrate and yeast. The yeast

provides enzymes, amylase and maltose, to breakdownthe complex carbohydrates into simple fermentablesugars (glucose and fructose). Zymase, another enzyme,breaks down the sugars as part of the yeast’s naturalmetabolic process of anaerobic respiration.

Ethanol and carbon dioxide are by-products. The ethanol istoxic to yeast in higher concentrations and at about 12%ethanol, the yeast dies and the reaction stops.



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The Manufacture of Ethanol Continued

Enzymes are biological catalysts. Therefore thetemperature and pH have to be controlled toprevent them from becoming denatured.

Oxygen must be excluded from the reaction so thatthe carbohydrates respire anaerobically and notaerobically. Moreover, oxygen allows for theoxidation of ethanol to form ethanoic acid

instead of alcohol. This process is usedindustrially as well as in the manufacture ofdrinks.



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The Reactions of Ethanol

1. Oxidation of EthanolEthanol burns readily in air and is sometimes used as a fuel. The

equation for the complete combustion of ethanol is:C2H5OH (l) + 3 02(g) 2 C02 (g) + 3H20 (g)

Strong oxidizing agents such as acidified potassium manganate(vii) or potassium dichromate (vi) will form organic(carboxylic) acids when it reacts with alcohols eg. ethanol. Anintermediate alkanal is formed in these reactions.

When ethanol reacts with acidified potassium permanganate,ethanoic acid is formed and there is a colour change from

purple to colourless.When ethanol reacts with acidified potassium dichromate,ethanoic acid is formed and there is a colour change fromorange to green.



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The Reaction of Ethanol Continued

2. Reacting Ethanol with sodiumDry ethanol reacts with sodium giving off hydrogen. A

white solid is left that has the formula C2H5ONa and iscalled sodium ethoxide. The equation for the reaction is:

2C2

H6

O (l) + 2Na

2CH5

ONa (s) + H2

(g)In the reaction of ethanol with sodium, only one of sixhydrogen atoms in the molecule is replaced. Hence thenecessary condition for this reaction is that the metalshave to be high in the electrochemical series ( morereactive) to react with lower alcohols so the metal willdisplace the hydrogen of the OH and the product will behydrogen gas and alkoxides which is a salt of thealcohol.



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3. Combustion of Ethanol

When alcohols burn they produce carbon dioxideand water. These reactions are very exothermic,

hence producing a lot of heat.C2H5OH (l) + 3O2 (g)2CO2 (g) + 3H2O(g) + HEAT

The necessary condition for this reaction is that it

has to take place under a “clean” flame or a blueflame.



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4. The dehydration of ethanol

The dehydration of alcohols

forms the alkenes. Therefore dehydrating ethanol will formethene and water.

H2OC2H5OH C2H4 + H20

H2SO4

This is done either by heating the ethanol with excesssulphuric acid at a temperature of 170°C, or by passing

the ethanol vapour over activated alumina at atemperature of 450°C. The condition necessary for thisreaction to take place is that the sulphuric acid has to beconcentrated.



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5. The reaction of ethanol with acids

The reaction of ethanol with acids will form esters.The general equation for this is:

Acid + alcohol ester + waterThis is reaction is reversible and so esters can be

hydrolyzed, however aqueous hydrolysis is a

very slow process. The hydrolysis of an ester iscatalyzed by acids; however the most effectiveway to catalyze an ester is with a strong alkali.



25

Quiz



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Quiz

1. What is the functional group of alcohols?

A: The hyroxyl group, -OH.

2. Define a carboxylic acid.

A: An organic compound containing the carboxyl group.

3. What does an ester consist of?

A: It consists of an acid in which at least one hydroxylgroup (-OH) is replaced by an alkyl (-O) group.

4. What is the general formula of alcohols?

A:CnH2n+1OH 5. Do esters have high or low melting and boiling points?

A: They have low melting points.



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Quiz Continued

6. Where are ester long chain acids found?

A: In vegetable oils and animal fats.

7.What type of esters have pleasant aromas?

A: Short chain esters.

8. Organic compounds of which homologous series act wellas solvents?

A: Alcohols act as excellent solvents.

9. Why can alcohols be used as fuels?

A: When alcohols combust they release energy.10. How do carboxylic acids react with metals?

A: They produce salt and hydrogen gas.



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Quiz Continued

11. How many reactions are there with ethanol?A: There are 5 reactions.12. What products are formed during a combustion

reaction with an alcohol?

A: Carbon dioxide, steam and heat.13. What temperature is necessary for dehydratingethanol?

A: Ethanol must be heated with sulphuric acid at 170°Cand passed over the alumina at 450°C.

14. What role will sulphuric acid play in convertingalcohols to esters?A: It acts as a catalyst.



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Quiz Continued

15. Is it necessary for the metal used in thereaction with ethanol to be high in theelectrochemical series?

A: Yes, for displacement.



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Scores:

15-12 correct: Great work!!

11-9 correct: Keep working at it!

Less than 9 correct: You need to

revisit this topic.



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References

Norman Lambert and Marine Mohammed,Chemistry for CXC, Heinemann EducationalPublishers, 1993

Anne Tindale, Chemistry: A Concise Revision

Course for CXC, Stanley Thornes (Publishers)Limited, 1998Karlene Bisnott, CXC Lecture Series

CHEMISTRY, Jamaica Observer Limited, 1998

Joanne Nazir, CHEMISTRY EXPLAINED ( AC.X.C COURSE), Unique Publishing HouseLimited, 2001

alcohols esters and carboxylic acids 2

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