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Organic Chemistry AS Level ~☆Sabrina Belfi ♡♡♡ > Chapter 17 : Alcohols, Esters and Carboxylic acids > Flashcards

Chapter 17 : Alcohols, Esters and Carboxylic acids Flashcards

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1
Q

Definition of primary alcohol

A

An alcohol in which the carbon atom bonded to the -OH group is attached to one other carbon atom (or alkyl group).

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2
Q

Definition of secondary alcohol

A

An alcohol in which the carbon atom bonded to the -OH is attached to two other carbon atoms (or alkyl groups).

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3
Q

Definition of tertiary alcohol :

A

An alcohol in which the carbon atom bonded to the -OH group is attached to three other carbon atoms (or alkyl groups)

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4
Q

Definition of biofuels :

A

Renewable fuels, sourced from plants or animal materials

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5
Q

Definition of esterification

A

The reaction between an alcohol and a carboxylic acid (or acyl chloride ) to produce an ester and water

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6
Q

Definition of dehydration

A

A reaction in which a water molecule is removed from a molecule, e.g. In the dehydration of an alcohol to give an alkene.

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7
Q

What is alcohol’s functional group?

A

-OH

A hydroxyl group

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8
Q

What is alcohol’s general formula?

A

CnH2n+1OH

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9
Q

Alcohol’s are named by adding what to the alkane stem?

A

‘-anol’

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10
Q

Why do alcohol’s have high BP , even methanol with the lowest molar mass is liquid at room temperature?

This is the same reason that smaller alcohol molecules mix and can dissolve in liquid well

A

Hydrogen bonding between alcohol molecules

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11
Q

What are the 6 reactions of the alcohols?

A
  1. Combustion
  2. Substitution to form a halogenoalkane
  3. Reaction with sodium metal
  4. Esterification
  5. Dehydration
  6. Oxidation
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12
Q

Combustion of an alcohol :

Write the general equation

A

Alcohol + Oxygen ➡ Carbon dioxide + water

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13
Q

What is a good substitute for fuel ?

A

Ethanol

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14
Q

Explain simply the industrial process of making ethanol

A

The glucose is sugar cane is fermented to make ethanol

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15
Q

Ethanol is an example of what kind of fuel ?

A

A biofuel

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16
Q

Why ethanol a better substitute to fuel ? 2 reasons

A
  1. Because it is ‘carbon neutral ‘ . Overall it does not increase the greenhouse gases in the air (in theory ).
  2. Use of ethanol conserves the world’s diminishing supplies of crude oil.
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17
Q

Name two uses of ethanol:

A
  1. As a biofuel

2. As a solvent

18
Q
  1. Substitution of an alcohol to form a halogenoalkane
  2. What is the general equation ?
  3. What are the 2 conditions ?
  4. what atom or group of atoms is replaced by what ?
  5. What makes the carbon open to nucleophilic attack?
  6. What is the nucleophile?
A
  1. Alcohol + hydrogen halide ➡ halogenoalkane + water
  2. Alcohol must be heated under reflux with an hydrogen halide (reactant )
  3. The OH group is replaced by the halogen atom
  4. The carbon atom bonded to the OH will carry a s+ (as O is more electronegative ) making it open to nucleophilic attack
  5. The nucleophile is the s- halogen atom in the Hydrogen halide
19
Q
  1. Substitution of an alcohol to form a halogenoalkane

What 3 compounds can be use instead of a hydrogen halide to substitute an alcohol and form a halogenoalkane? Plus equations

A
  1. Sulfur dichloride Oxide , SOCl2

Reaction : C2H5OH + SOCL2 ➡ C2H5CL + HCL (g) + SO2 (g)

                      🌟 2. Phosphorus(V)  halides, e.g. Phosphorus  (V) chloride , PCL5 

                                             Room temp. Reaction :   C2H5OH + PCL5         ➡           C2H5CL + HCl  (g)+ POCL3 

                          🌟 3.   Phosphorus  (III) Halides e.g. PI3 ........Phosphorus (III) is red in colour 

                                                 HEAT Reaction :  3 C2H5OH  + PI3       ➡       3 C2H5I    + H3PO3 
                                                             iodoethane
20
Q
  1. Reaction of an alcohol with sodium metal
  2. What bond breaks ?
  3. Is the reaction more or less vigorous than the reaction between sodium and water?
  4. What is the general equation
  5. What two products are formed?
  6. Example of ethanol and sofium
A
  1. The O-H bond in the alcohol breaks
  2. This reaction is less vigorous than if water was used instead of alcohol
  3. Alcohol + sodium ➡sodium alkoxide + hydrogen
  4. Hydrogen gas and a basic ionic compound (called, sodium alkanestem-oxide e.g. sodium propoxide)
  5. C2H5OH + Na ➡C2H5O^-Na^+ +H2
    Ethanol sodium ethoxide
21
Q

What is esterification?

A

The making of esters from carboxylic acids and alcohols

22
Q

Description of esters and 3 uses in industry

A

Esters usually have sweet , fruity smells . They are present naturally in fruits.

Uses:

  1. artificial flavouring
  2. Perfumes
  3. As solvents , e.g. In nail Polish remover
23
Q
  1. Esterification
  2. What bond breaks
  3. What is the general equation
  4. What are the 2 conditions
  5. An example of esterification using ethanol and ethanoic acid
A
  1. The O-H bond in the alcohol breaks
  2.                                   Acid catalyst, heat under reflux    Carboxylic acid + alcohol                 ↔                 ester + water 
                                                   Reversible
  3. Conditions :

● Heated under reflux

●acid catalyst (usually sulfuric acid)

  1.                                            H2SO4  C2H5OH    +    CH3C⚌O              ↔              CH3C⚌O                 +    H2O 
                            \                                                 \  
                             OH                                             OC2H5  ethanol                ethanoic acid                        ethyl ethanoate              water
24
Q

How to name esters :

Using ethanol and ethanoic acid to form ab ester as the example

A

●first part of the name comes from the alcohol e.g. ethanol giving “ethyl “

● the second part comes from the carboxylic acid , e.g. ethanoic acid giving “ethanoate”

So ethyl ethanoate

25
Q

Hydrolysis if an ester is the reverse of …..

A

Esterification

26
Q

Hydrolysis of esters:

What 2 conditions have to be met to be able to hydrolyse an ester?

A

Heating under reflux with either an acid or a Base

27
Q

What are the two differences if you hydrolyse an ester with a acid or with a alkali

A
  1. 😍Heating under reflux with an acid is a reversible reaction whilst (condition H^+(aq))🤔heating under reflux with an akali is irreversible, so the ester can be broken down by excess alkali
  2. 😍In acid hydrolysis there is always both reactants (ester +water) and both products (alcohol + ester )🤔 in alkali hydrolysis the reactants are the ester + NaOH (alkali) and the product is an alcohol + sodium salt of the carboxylic acid.
28
Q

Use ethyl ethanoate and NaOH to show the alkali hydrolysis of esters

A

H3C-C⚌O
\ + NaOH ➡ H3C-C⚌O + CH3CH2OH
O - CH2CH3 \
O- Na^+
Ethyl ethanoate sodium ethanoate ethanol

29
Q
  1. Dehydration (elimination ) of alcohols
  2. What small molecule is removed from the alcohol ?
  3. What is the general equation?
  4. What 3 things can catalyse this reaction ?
  5. An example using the dehydration of ethanol
A
  1. H2O
  2. Catalyst
    Alcohol ➡ alkene + water
  3. Catalysts = ● hot aluminium oxide powder , Al2O3 😍😍😍😍😍😍😍😍😍1st choice catalyst
                      ● pieces of porous pot

                  ● pumice 
  4.              Al2O3 catalyst   C2H5OH                 ➡              C2H4   +    H2O
30
Q
  1. Oxidation of alcohols

How can a primary alcohol be oxidised to an aldehyde? 2

A
  1. Heating gently with acidified potassium dichromate (VI), K2Cr2O7 -acidified with dilute sulfuric acid
  2. Distilling out the aldehyde as it forms ( so that it doesn’t oxidise further )
31
Q
  1. Oxidation of alcohols

How can an alcohol be further oxidised into a carboxylic acid ? (2)

A
  1. Refluxing the alcohol with
  2. Excess acidified K2Cr2O7 (acidified with sulfuric acid)

(The aldehyde cannot get out so it is further oxidised )

32
Q
  1. Oxidation of alcohols

How can a ketone be formed ?

A

By heating a secondary alcohol with acidified K2Cr2O7 which oxidises it (reaction mixture turns green)

33
Q

Acidified K2Cr2O7 changes from what colour to what colour when a primary or secondary alcohol is oxidised by it ?

A

From orange to green

34
Q

What type of alcohol cannot be oxidised by refluxing with acidified potassium dichromate?

A

Tertiary alcohols ( mixture of them would remain orange )

35
Q

Carboxylic acids:

What are the 3 ways in which carboxylic acids can be formed ?

A

1 and 2 . Oxidation of primary alcohols or aldehydes by refluxing with excess potassium dichromate (VI) and dilute sulfuric acid

  1. By refluxing nitriles with dilute hydrochloric acid
36
Q

Why are carboxylic acids considered weak acids?

A

Because their molecules do not dissociated (ionise) completely when added to water

37
Q

The presence of H^+ (aq) ions in solutions of carboxylic acids mean that they undergo all the usual reactions of acids :

  1. What is their salt referred to?
  2. Give the general equation of its reaction with alkali
  3. Give the general equation of its reaction with metals
  4. Give the general equation of its reaction with carbonates
  5. Give an example of a salt formed using Na for the general structure of the salt
A
  1. Carboxylate salts
  2. Carboxylic acid + alkali ➡ Carboxylate salt + water
  3. Carboxylic acid + metal ➡ Carboxylate salt + hydrogen gas
  4. Carboxylic acid +carbonate ➡ Carboxylate salt + water +Carbon dioxide
  5. Example of the structure of a carboxylate salt :CH3COONa , sodium ethanoate

Or e.g. (CH3COO)<2 Mg ⊙ two times the what’s in the brackets and Mg

38
Q

What can reduce carboxylic acids to form primary alcohols? 3 conditions

A
  1. LiAlH4 (tetrahydridoaluminate) in dry ether

2. Room temperature

39
Q

Why is dry ether used in the reduction of carboxylic acids?

A

Because LiAlH4 reacts violently with water

40
Q

Show the equation of ethanoic acid being reduced to ethanol

A

LiAlH4 in dry ether

CH3COOH + 4H ➡ CH3CH2OH + H2O

Organic Chemistry AS Level ~☆Sabrina Belfi ♡♡♡ (5 decks)

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