alcohols a level chemistry

8/20/2019 Alcohols A Level chemistry

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What are alcohols?

Alcohols are a homologous series of organic compounds

with the general formula CnH

2n

+1

H and names ending !ol "

#he functional group in alcohols is the hydroxyl group$ !H"

C%H11H pentanol

C&H9H 'utanol

C3H(H propanol

C2H%H ethanol

CH3H methanol

C)H13H he*anol

%

&

3

2

1

NameNo. of carbon atoms

Molecular

formula

)


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Naming alcohols

lcohols with three or more car'on atoms displa,

positional isomerism" #he num'er of the car'on to which

the h,dro*,l groups is attached is written 'efore the !ol "

propan-1-ol propan-2-ol


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Alcohols and hydrogen bonding

#he presence of the h,dro*,l

group with its electronegati-e

o*,gen atom means that

alcohols are polar" #he, can

therefore take part in

h,drogen 'onding"

H,drogen 'onding 'etween alcohol molecules means that

an alcohol.s 'oiling point is higher than that of an alkane of

similar molecular mass" /or e*ample methanol M r 32

'oils at )&"( 4C 'ut ethane M r 30 'oils at 566") 4C"

lcohols can mi* with water 'ecause their molecules can

form h,drogen 'onds with water molecules"


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Making ine and cider

lcohol has 'een produced

', fermentation of sugars

for thousands of ,ears"

7ugar from fruit or grains

such as wheat and 'arle, ismi*ed with ,east and water

which produces ethanol and

other compounds"


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!ndustrial fermentation

8ndustriall, sugar cane

molasses a product of refining

sugar cane or starch from

potatoes or corn can 'e used

for fermentation"

#he product is a mi*ture ofwater and a'out 1% ethanol

', -olume" :o more alcohol is

produced 'ecause the ,east is

denatured ', the alcohol"

;istillation can 'e used to

remo-e most of the water

from the ethanol"


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"roduction of ethanol from ethene


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#ermentation $s. hydration



chain of car'on atoms can 'e represented ', < when

drawing the structure" #his is referred to as an % group"

"rimary& secondary and tertiary

"rimary '1() alcohols ha-e one

< group attached to the car'on to

which the H group is attached"

*econdary '2() alcohols ha-e two

< groups attached to the car'on to


+ertiary ',() alcohols ha-e three

< groups attached to the car'on to




xidation of 1( alcohols aldehydes

"rimary alcohols can 'e o*idi=ed to aldehydes ', an

o*idi=ing agent such as an a>ueous solution of acidified

potassium dichromate?8"

ldeh,des contain a car'on,l

group C at the end of the

car'on chain and are named

using the suffi* !al "

@hen the s,m'ol e>uation is written the o*idi=ing agent is

represented ', A$

%/020 3 %/0 02

propanal



*ynthesis of aldehydes

@hen aldeh,des are prepared ', the

reaction of a primar, alcohol with

acidified potassium dichromate?8

the aldeh,de is distilled off and

collected pre-enting further o*idation"

heat

ater in

ater out

mixture of

alcohol&

dilute sulfuric

acid and

potassium

dichromate'4!)

aldehyde

ice


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xidation of 1( alcohols carboxylic acids

8f primar, alcohols are reacted with an e*cess of o*idi=ing

agent and refluxed the, can 'e o*idi=ed to aldeh,des and

then o*idi*ed further to carboxylic acids"

Car'o*,lic acids contain a car'on,l group C at the end

of the car'on chain with a h,dro*,l group H attached to

the car'on,l car'on"

Car'o*,lic acid are named

using the suffi* !oic acid "

%/020 3 %/0 02 %/0 3 %/0

propanoic acid


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*ynthesis of carboxylic acids


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xidation of 2( alcohols ketones

*econdary alcohols can 'e o*idi=ed to ketones ', an

o*idi=ing agent such as an a>ueous solution of acidified

potassium dichromate?8"

etones contain a car'on,lgroup C attached to an,

car'on in the chain e*cept a

terminal car'on atom and are

named using the suffi* !one"propanone

%1/0'0)%2 3 %1/%2 02

+ertiary alcohols are resistant to o*idation due to the

lack of h,drogen atoms on the car'on atom to which

the h,dro*,l group is attached"


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Aldehyde& ketone or carboxylic acid?



5istinguishing aldehydes and ketones



6sterification

6sterification in-ol-es reflu*ing a car'o*,lic acid and an

alcohol with a concentrated sulfuric acid catal,st"

#he names of esters ha-e

two parts$ the first is an

alk,l group from the

alcohol and the second is

a car'o*,late group from

the car'o*,lic acid" fromalcohol

fromcarboxylic acid

/or e*ample methanol and ethanoic acid react to form

meth,l ethanoate"

%1/0 %20 %1/%2 02



xidation of alcohols



Making alcohols from aldehydes7ketones

ldeh,des and ketones can 'e reduced ', a reducing agent

such as sodium 'oroh,dride :aBH& to form alcohols"

@hen the s,m'ol e>uation is written the reducing agent is

represented ', AH"

ldeh,des are reduced to primar, alcohols$

etones are reduced to secondar, alcohols$

%1/0%2 03 %1/0'0)%2

%/0 203 %/020



*ynthesis of ethene from ethanol


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5ehydration of ethanol in the lab

8n the la' deh,dration of ethanol can 'e achie-ed ',

passing ethanol o-er a hot aluminium o*ide catal,st"

Dthene gas is collected ', displacement"

ethene gas

aluminium

oxide

ceramic ool soaked

in ethanol

ater


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/ombustion of alcohols

lcohols undergo complete com'ustion to form car'on

dio*ide and water"

;enatured alcohol is a useful porta'le fuel e"g" for camping

sto-es as unlike LEF it does not need to 'e transported in

hea-, speciali=ed containers" 8t is also used as a sol-ent"

5enatured alcohol is ethanol that has 'een made to*ic andundrinka'le ', the addition of other chemical additi-es"

traditional additi-e was methanol which formed

methylated spirits meths$ 90 ethanol and 10 methanol"

/0,/020 ,2 2/2 ,02


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#orming halogenoalkanes from alcohols

Erimar, secondar, and tertiar, alcohols all react with

phosphorus? chloride to form a chloroalkane" /or e*ample$

dding solid phosphorous? chloride to an alcohol at

room temperature produces white HCl fumes as well as

the chloroalkane"

#his reaction can 'e used as a test for alcohols the H

group as well as a method of producing halogenoalkanes"

/0,/020 "/l8 /0,/02/l "/l, 0/l

Al h l i


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Alcohol reactions


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9l


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9lossary

Wh t: th k d?


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What:s the keyord?

Wh t: th t t ?


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What:s the structure?

M lti l h i i


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Multiple-choice ;ui

alcohols a level chemistry

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