Unit 2.7 - Alcohols and carboxylic acids Flashcards
Alcohols
Compounds with one or more hydroxy (OH) groups attached to the aliphatic (straight) chain
How do we name an alcohol?
Add -ol to the alkane stem
Why and where would we put numbers in the names of alcohols?
From ethanol onwards, we need to specify the position of the hydroxy group
Hydroxy group
OH
What are the three groups which alcohols can be classified into?
Primary (1°), Secondary (2°), Tertiary (3°)
What can be classified as primary, secondary and tertiary?
Halogenoalkanes
Alcohols
Primary alcohols
The carbon which carries the OH group is only attached to 1 alkyl group (1 other carbon atom)
Alkyl group
Carbon atom group
What type of alcohol is ethanol?
Primary
What type of alcohol is propan-1-ol?
Primary
What type of alcohol is 2-methylpropan-1-ol?
Primary
What type of alcohol is propan-2-ol?
Secondary
What type of alcohol is butan-2-ol?
Secondary
What type of alcohol is pentan-3-ol?
Secondary
What type of alcohol is 2-methylpropan-2-ol?
Tertiary
What type of alcohol is 2-methylbuan-2-ol?
Tertiary
Secondary alcohols
The carbon which carries the OH group is attached to 2 alkyl groups (which may be the same or different)
Tertiary alcohols
The carbon which carries the OH group is attached to 3 alkyl groups (which may be any combination of same or different)
Name some physical properties
Melting and boiling point
Solubility
Describe the solubility of alcohols
The lower alcohols (shorter chain) are completely soluble in water (are able to form hydrogen bonds with water)
As the alkyl (hydrocarbon) chain increases in length, the contribution of the hydrogen bond to the overall intermolecular forces decreases, so the higher alcohols from butanol onwards are not very soluble in water
Lower alcohols
Shorter chain
Which alcohols are completely soluble in water and why?
Lower alcohols (shorter chain)
Are able to form hydrogen bonds with water
Which alcohols are less soluble in water and why?
The higher alcohols (longer chain) from butanol onwards
As the alkyl (hydrocarbon) chain increases in length, the contribution of the hydrogen bond to the overall intermolecular forces decreases
Alkyl chain
Hydrocarbon chain
Draw hydrogen bonding between ethanol and water
(See notes)
Why do alcohols form hydrogen bonds with water?
Highly polarising 𝛿+ hydrogen atom attracts a lone pair of electrons from a small, highly electronegative atom in another molecule (N, O, F)
(O in this case)
Describe the boiling points of alcohols
Alcohols have higher boiling points than alkanes of similar molar mass due to hydrogen bonding
Why do alcohols have higher boiling points than alkanes of similar molar mass?
Alcohols contain hydrogen bonding
Which bonds break when a covalent compound is boiled?
Intermolecular forces (Van der Waal, hydrogen bonding)
NOT Intramolecular forces (covalent, ionic, coordinate)
Compare the boiling points of alcohols to those of alkanes of similar molar mass in terms of intermolecular forces
Alkanes intermolecular forces = only induced dipole-induced dipole
Alcohols intermolecular forces = additional hydrogen bonding that elevate the boiling temperature
Draw the hydrogen bonds between ethanol and other ethanol molecules
(See notes)
Why does ethanol have a high boiling point?
The hydrogen bonds require a significant amount of energy to break
What is ethanol soluble in?
Water
Non-polar solvents
Why is ethanol soluble in non-polar solvents?
Due to the presence of the hydrocarbon chain
Why is ethanol an extremely important solvent?
Soluble in both water and non-polar solvents
What are the 2 methods for the preparation of alcohols?
From alkenes
By fermentation
How is ethanol reduced by an alkene?
Steam hydrolysis of ethene
What does the steam hydrolysis of ethene produce?
Ethanol
Conditions for the production of ethanol from ethene via steam hydrolysis?
Phosphoric acid catalyst/concentrated sulphuric acid
300 degrees Celsius
60 atm pressure
Write the equation for the formation of ethanol via the steam hydrolysis of ethene
CH2=CH2 + H2O (g) —> CH3CH2OH
What type of reaction is the steam hydrolysis of ethene to form ethanol?
Electrophilic addition
If ethanol is made by fermentation, what are the 2 processes required?
Fermentation
Distillation
What happens during fermentation?
Sugars (glucose) from plants are converted into ethanol by the action of enzymes in the yeast (zymase)
Enzymes in yeast
zymase
Equation for the fermentation of glucose to form ethanol
C6H12O6 (aq) —> 2C2H5OH (aq) + 2CO2 (g)
What’s the temperature used during fermentation to form ethanol and why?
The rate of this reaction is affected by temperature
At low temperatures, it’s slow
At high temperatures, it can denature the enzymes
The compromise is 35 degrees Celsius
Describe the conditions of the reaction vessels for fermentation to occur to create ethanol and explain why this is necessary
Air must be kept out of the reaction vessel
If not m ethanol will react (oxidise) and form ethanoic acid (vinegar)
What is done following fermentation to produce ethanol?
Distillation
When and how is ethanol distilled off the mixture following fermentation?
Once the solution contains 15% ethanol, fermentation stops and the ethanol is distilled off the mixture using fractional distillation
What’s the boiling point of ethanol?
78 degrees Celsius
Batch process
When the process has to be stopped and restarted
What’s the name of a process that has to be stopped and restarted?
Batch process
What type of process is fermentation to produce ethanol and why?
Batch process
The process has to be stopped and restarted
Draw the label the apparatus required for distillation
(See notes)
Why do we need a fractioning column when producing ethanol?
We need to separate hydrocarbons of similar boiling temperatures
Biofuels
Fuels that are produced from living organisms (plants, microorganisms)
2 main types of biofuels currently used
Bio ethanol
Bio diesel
What’s bioethanol obtained from?
Sugars in plants by fermentation
What’s biodiesel obtained from?
Oils and fats present from the seeds of some plans
How do both bioethanol and biodiesel burn and why is this significant?
Exothermically
Are good heat sources
Can be used as fuels
Advantages of biofuels
Renewable
Carbon neutrality
Economic and political security
Why are biofuels better than fossil fuels in terms of how renewable they are?
Fossil fuels will eventually run out
However…
Plants can be grown each year
Can produce biofuels using waste material from animals
Why is using biofuels as a fuel carbon neural?
Although CO2 is produced in exactly the same way by biofuels and fossil fuels when combusted, CO2 is taken in by plants when they grow via photosynthesis to produce sugars
Equation for plants photosynthesising to achieve carbon neutrality with biofuels
6CO2 + 6H2O —> C6H12O6 + 6O2
How do biofuels provide economic and political security?
Countries that do not have fossil fuels as a natural resource are less dependant on changes in price and availability tat having to import fossil fuels imposes
Disadvantages of biofuels
Land use
Use of resources
Carbon neutrality ???
How is land use a disadvantage to biofuels?
Land that is used to produce plants for biofuels cannot be used to produce food
Destroying environmentally significant areas (e.g - forests) to create land for biofuel production
Which resources are large quantities of needed for biofuels?
Large quantities of water and fertilisers
Why is the large use of water for biofuels bad?
Strains local resources
How can water become polluted using biofuels?
The use of large quantities of fertilisers to grow the same crop year after year
What effect can using fertilisers year after year for biofuels have?
Polluted water
Why is using biofuels not certainly carbon neutral?
When the fuel needed to build and run the factories needed in biofuel production (e.g - to transport new materials and finished products) are considered, it can be argues that the use of such fuels is not carbon neutral
What are the 2 chemical reactions of alcohols?
Oxidation
Dehydration
Oxidise agent for the oxidation of alcohols
Potassium dichromate (VI) acidified with concentrated sulphuric acid
Equation for acidified dichromate
H+/CrO7^-2
Equation for acidified potassium dichromate
H+/K2Cr2O7
What has to occur to the mixture for the oxidation of alcohols?
Has to be heated
The oxidation of what occurs in 2 stages?
Primary alcohols
Stages of oxidising a primary alcohol
1 - mild oxidation to produce an aldehyde
2 - further oxidise the aldehyde under reflux to produce a carboxylic acid
How does the first stage of the oxidation of a primary alcohol occur?
With heat
Distilled
Equation for the first stage of the oxidation of ethanol, a primary alcohol
(See notes)
What occurs during the second stage of the oxidation of a primary alcohol?
The aldehyde is oxidised further under reflux
What is produced at the first and second steps of the oxidation of primary alcohols?
1 - aldehyde
2 - carboxylic acid
Write the equation for the second stage of the oxidation of ethanol, a primary alcohol
(See notes)
Draw a diagram to summarise the oxidation of ethanol, a primary alcohol
(See notes)
What happens to the dichromate ion (VI) during the oxidation of the primary alcohol, ethanol?
It’s reduced to the chromium (III) ion
We see this as a colour change from orange to green
Why do we see a colour change during the oxidation of a primary alcohol and what is this colour change?
During the reaction, the dichromate (VI) ion, CrO7^2- is reduced to the chromium (III) ion, Cr^3+
Colour change form orange to green
What are the stages that occur during the oxidation of secondary alcohols?
Only one stage - oxidation
Write the equation for the oxidation of propan-2-ol, a secondary alcohol
(See notes)
What’s the product of the oxidation of a secondary alcohol?
A ketone
Ketone functional group
C=O
Aldehyde functional group
C =O
- H
What are the steps in the oxidation of tertiary alcohols?
Since there is no hydrogen on the adjacent carbon atom that can be lost, no reaction takes place
Why does no reaction occur during the oxidation of tertiary alcohols compares to primary and secondary alcohols?
Since there is no hydrogen on the adjacent carbon atom that can be lost, no reaction takes place.
Only primary and secondary alcohols (and aldehydes) have an oxidisable hydrogen
What have an oxidisable hydrogen?
Primary alcohols
Secondary alcohols
Aldehydes
What happens during the dehydration of primary alcohols?
Primary alcohol is reacted with concentrated sulfuric acid in excess
What is a primary alcohol reacted with for its dehydration?
Concentrated sulfuric acid in excess
Temperature for the dehydration of primary alcohols
170 degrees Celsius
Main product of the dehydration of primary alcohols
Alkene
What does the sulfuric acid do during the dehydration of primary alcohols?
Removes the elements of water form the alcohol
Write the equation for the dehydration of ethanol, a primary alcohol
CH3CH2OH ⇌ CH2 = CH2 + H2O
What type of reaction is the dehydration of primary alcohols?
Elimination reaction
What can we notice from the e hydration reaction of ethanol?
It’s the reverse of producing industrial strength alcohol
What can we use to test for primary and secondary alcohols?
Acidified dichromate solution
What happens when we use acidified dichromate solution to identify primary and secondary alcohols?
The primary alcohol gets converted to a carboxylic acid
The secondary alcohol gets converted into a ketone
The colour of the potassium dichromate (VI) cages from orange to green as the dichromate (VI) ion is reduced to the chromium (III) ion
Why is there a colour change fro orange to green when testing for primary and secondary alcohols?
The dichromate (V) ion is reduced to the chromium (III) ion
Why can’t we use acidified dichromate solution to test for tertiary alcohols?
They will not react with potassium dichromate
What does acidified dichromate solution help us identify and what’s the observation?
Primary and secondary alcohols (not tertiary)
Colour change form orange to green
What’s an alternative catalyst to concentrated sulfuric acid for the dehydration of an alcohol from an alkene?
Aluminium oxide
What type of sulfuric acid is used in the preparation of alcohols from alkenes?
Concentrated
Advantage of producing ethene from alkenes
100% atom economy
What is another way that bumping can be avoided apart from using anti-bumping granules?
Carrying the reaction out in a larger container
Carboxylic acids functional group
COOH
Draw the functional group of carboxylic acids
(See notes)
How do we name carboxylic acids?
Add -oic acid to the alkane stem
Methanoic acid common name
Formic acid
Formic acid
Methanoic acid
Ethanoic acid common name
Acetic acid
Acetic acid
Ethanoic acid
Glucose formula
C6H12O6
Give the graphical formula of Methanoic acid
(See noteS)
Give the skeletal formula of Methanoic acid
(See notes)
Give the graphical formula of ethanoic acid
(See notes)
Give the skeletal formula of ethanoic acid
(See notes)
Shortened structural formula of Methanoic acid
HCOOH
Shortened structural formula of ethanoic acid
CH3COOH
Where do we get Methanoic/Formic acid?
Released by stinging ants
What do ants release when stinging?
Methanoic/Formic acid
Where do we get ethanoic/acetic acid?
Vinegar
What type of acid is in vinegar?
Ethanoic/acetic
Why are carboxylic acids acidic?
They release H+ ions when added to water
Are carboxylic acids weak or strong acids?
Weak acids
Why are carboxylic acids weak acids?
They do not fully dissociate into their ions in aqueous solution - there’s often less than 1% dissociation
What happens as a result of carboxylic acids being weak acids?
The ionisation that is needed to produce the H+ is in equilibrium
Write an equation for the dissociation of a carboxylic acid into its ions
RCOOH ⇌ RCOO- + H+
How do carboxylic acids react with all in a similar way?
Bases, carbonates and hydrogen carbonates
How do carboxylic acids react with bases, carbonates and hydrogen carbonates?
In a similar way to strong inorganic acids such as hydrochloric acid
What type of acid is hydrochloric acid?
Strong inorganic acid
Salt
A chemical compound formed by ionic bonds between cations and anions
What makes up the salt in the neutralisation reaction between an acid and a base?
A metal ion from the base replaces the H+ ion in the acid to form a salt
What does the hydrogen ion in acid replace to form a salt?
Metal or ammonium ion
Worded equation for the reaction between an acid and a base
ACID + BASE ——> SALT + WATER
What is sodium hydroxide an example of?
A strong alkali
Alkali
Base that dissociates in water
What does ethanoic acid and sodium hydroxide form?
Sodium ethanoate
Equation for the reaction between ethanoic acid and sodium hydroxide
CH3COOH + NaOH —> CH3COONa + H2O
Ethanoate ion
CH3COO-
Which ion is CH3COO-?
Ethanoate ion
What does ethanoic acid react with copper (II) oxide to form?
Copper (II) ethanoate
Equation for the reaction between ethanoic acid and copper (II) oxide
2CH3COOH + CuO —> (CH3COO)2Cu + H2O
Worded equation for the reaction between acids and metals
ACID + METAL —> SALT + H2
What does the H2 formed when an acid reacts with a metal do?
Causes effervescence
What does magnesium react with propanone acid to form?
Magnesium propanoate
Write the equation for the reaction between propanoic acid and magnesium
2CH3CH2COOH (aq) + Mg (s) —> (CH3CH2COO)2Mg (aq) + H2 (s)
Propanoate ion
CH3CH2COO-
Charges on anions from carboxylic acids
-1
Write a worded equation for the reaction between carboxylic acids and carbonates/hydrogencarbonates
ACID + CARBONATE —> SALT + CARBON DIOXIDE + WATER
Write the equation between propanoic acid and copper cabonate
2CH3CH2COOH + CuCO3 —> (CH3CH2COOH)2Cu + CO2 + H2O
Write the equation for the reaction between Methanoic acid and sodium hydrogencarbonate
HCOOH + NAHCO3 —> HCOONa + CO2 + H2O
How can we test for the presence of carboxylic acids?
Using carbonate or hydrogencarbonate
What are the steps for testing the presence of a carboxylic acid?
- Addition of sodium carbonate/sodium hydrogencarbonate
- Effervescence can be observed - test for CO2 by checking if it turns limewater milky
Write the reaction between ethanoic acid and sodium hydrogencarbonate
CH3COOH + NAHCO3 —> CH3COONa + CO2 + H2O
Write the equation for the reaction between ethanoic acid and sodium carbonate
2CH3COOH + Na2CO3 —> 2CH3COONa + CO2 + H2O
What are the 2 types of reactions of carboxylic acids?
As an acid
Esterification
Esterification
Carboxylic acids react with alcohols to form an ester
What’s noticeable about an ester?
Sweet smelling
How do esters smell and what are they used for therefore?
Sweet smelling, used in fragrances
Functional group of esters
COO
What is COO the functional group of?
Esters
What are ester bonds important in?
Lipids
Draw the functional group of an ester
(See notes)
What’s the chemical formula of an ester?
RCOOR1
Where R is the alkane stem
Write the worded equation for the reaction between a carboxylic acid and alcohol
carboxylic acid + alcohol ⇌ ester + water
How is the carboxylic acid and alcohol added during esterification?
In equimolar amounts
what is required for the reaction between carboxylic acid and alcohol to occur?
concentrated sulfuric acid
why is it necessary to have concentrated sulfuric acid for the reaction between a carboxylic acid and an alcohol?
acts as a catalyst - the reaction would otherwise be very slow
powerful dehydrating agent = removes water from the equilibrium mixture
under which conditions is carboxylic acid added to alcohol during esterification?
reflux
what happens to the position of equilibrium during esterification?
as concentrated sulfuric acid removes water, the position of equilibrium moves to the right and the reaction goes to completion
when does the position of equilibrium move during esterification and in which direction?
as concentrated sulfuric acid removes water
moves to the right and the reaction goes to completion
write the chemical reaction between ethanoic acid and ethanol
CH3COOH + CH3CH2OH ⇌ CH3COOCH2CH3 + H2O
what is the esterification reaction also known as and why?
a condensation reaction as there’s a small molecule (water) lost
how is the ester separated from the mixture during esterification?
through distillation
which two processes are used during esterification?
reflux
distillation
why is distillation used during esterification?
to separate the ester
draw a diagram for reflux equipment
(See notes)_
draw and label a diagram for the distillation part of the esterification reaction
(see notes)
write the structural formula of the esterification reaction between ethanoic acid and ethanol
(See notes)
what is the name of an ester derived from?
from the names of the 2 reactants from which it formed
how do we name esters?
1st part - alcohol, with name changes to end with -yl
2nd part - carboxylic acid or acid anhydride, with name changed to end in -oate
explain why the ester methyl ethanoate is called this
methyl - comes from methanol, CH3OH
ethanoate - comes from ethanoic acid, CH3COOH
draw the structural formula for the esterification reaction between methanol and ethanoic acid
(See notes)
explain why the ester ethyl methanoate is called this
ethyl comes from ethanol, CH3CH2OH
methanoate comes from methanoic acid, HCOOH
what makes it easier to write the structural equations for the formation of an ester?
put the functional groups that are reacting facing each other
write the structural formula for the esterification reaction that forms 2-methylethylpropanoate
(see notes)
methanoic acid formula
HCOOH
What are the conditions required for the production of as ketone from a secondary alcohol?
Reflux
Cr2O7^2-/H+
Why is reflux used?
To avoid loss of reagents/ products
Does an aldehyde react with sodium carbonate? Why?
No
It’s not acidic
Does a ketone react with sodium carbonate? Why?
No
It’s to acidic
What is the catalyst when producing ethanol from the hydrolysis of ethane?
Phosphoric acid
What’s higher- the boiling point of a carboxylic acid or it’s corresponding alcohol? Why?
The boiling point of the carboxylic acid is higher
It forms stronger hydrogen bonds
Under which condition do we use acidified potassium dichromate to test for the presence of a primary or secondary alcohol?
Under reflux
In what condition is the water in the production of ethanol from ethane?
Steam
Describe the method for preparing a sample of ethanal by oxidising ethanol
Acid and dichromate until it dissolves
Cool mixture and add ethanol dropwise (shaking between additions)
Set up distillation apparatus
Heat gently until liquid bois over
Describe the boiling points of esters and explain
Low as they don’t form hydrogen bonds
Which carbons are counted and for naming what when naming an ester?
Carbons after COO group —> alcohol (-yl)
Carbons up to and including COO group —> carboxylic acid (-oate)
What causes the colour change to green in oxidation of alcohols reactions?
The chromium ion
What do you do about the side groups present when naming esters?
Name them as you would normally (first)
What else can acidified dichromate be used to test for except primary and secondary alcohols?
Aldehydes
What type of property is the fact that esters have a sweet smell?
Physical property
Why are enzymes good in terms of green chemistry in reactions?
Bring down the energy required
Which mass do we use in percentage yield questions as the theoretical mass?
The least mass
