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Organic Chemistry (Year 1) > Alcohols > Flashcards

Alcohols Flashcards

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1
Q

General formula for alcohols

A

CnH2n+1OH

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2
Q

Alcohol name ending?

A

-ol.

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3
Q

Alcohol prefix?

A

Hydroxy-

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4
Q

How would you name an alcohol with 2 or more OH groups?

A

Diol or Triol but leave the e on the alkane.

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5
Q

Describe the boiling point of alcohol?

A

They have low volatility and high boiling points due to their ability to form hydrogen bonds between alcohol molecules.

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6
Q

Why can smaller alcohols dissolve in water?

A

Because they can form hydrogen bonds to water molecules.

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7
Q

What is a primary alcohol?

A

1 carbon is attached to the carbon that is attached to the oxygen.

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8
Q

What is a secondary alcohol?

A

2 carbons are attached to the carbon that is attached to the oxygen.

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9
Q

What is a tertiary alcohol?

A

3 carbons are attached to the carbon that is attached to the oxygen.

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10
Q

What oxidising agent is used for alcohols?

A

Potassium dichromate.
K2Cr2O7

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11
Q

If you partially oxidise a primary alcohol what do you get?

A

Aldehyde

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12
Q

What reagents are used for the partial oxidation of a primary alcohol?

A

Potassium Dichromate (VI) and Dilute Sulfuric Acid

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13
Q

What conditions are needed for the partial oxidation of a primary alcohol?

A

Warm gently and distil out the aldehyde as it forms.

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14
Q

What is the name ending of an aldehyde?

A

-al

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15
Q

Where is the C=O bond of an aldehyde?

A

On the first carbon.

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16
Q

What is the observation in a partial oxidation of a primary alcohol?

A

The orange Dichromate ion (Cr2O7^2-) reduces to the green Cr^3+ ion.

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17
Q

Do you need to add a number when writing the aldehyde name?

A

No because the aldehyde functional group is on the end of the carbon chain always.

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18
Q

When writing the structural formula of an aldehyde, how do you write the aldehyde group?

A

CHO

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19
Q

What is the structural formula of propanal?

A

CH3CH2CHO

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20
Q

What is formed in the full oxidation of a primary alcohol?

A

Carboxylic acid

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21
Q

What reagent is needed for the full oxidation of a primary alcohol?

A

Potassium Dichromate (VI) solution and dilute sulfuric acid.

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22
Q

What conditions are needed for the full oxidation of a primary alcohol?

A

Use an excess of potassium dichromate and heat under reflux.

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23
Q

What is the observation for the full oxidation of a primary alcohol?

A

The orange Dichromate ion (Cr2O7^2-) reduces to the green Cr^3+ ion.

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24
Q

What is formed in the oxidation of secondary alcohols?

A

Ketone

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25
What reagents are needed in the oxidation of secondary alcohols?
Potassium Dichromate (VI) and Dilute sulfuric acid.
26
What conditions are needed in the oxidation of secondary alcohols?
Heat under reflux.
27
Ketone name ending?
-one
28
Can a secondary alcohol be further oxidised after becoming a ketone?
No
29
What is formed for every oxidation ?
Water molecule
30
Why can't tertiary alcohols be oxidised by potassium dichromate?
There is no H atom bonded to the carbon with the OH group.
31
How can the presence of a carboxylic acid be tested?
By adding sodium carbonate. It will fizz and produce carbon dioxide.
32
What are the two tests to test for aldehydes and ketones?
Tollens' reagent and Fehling's solution
33
What does Fehling's solution contain?
Blue Cu^2+ ions
34
What are the conditions for Fehling's solution?
Heat gently
35
What reaction occurs in Fehling's solution?
Aldehydes only are oxidised by Fehling's solution into a carboxylic acid. The Cu^2+ ions are reduced to Copper(I) Oxide.
36
What is observed in the reaction with Fehling's solution?
For aldehydes, the blue Cu^2+ ions in the solution change to a red precipitate of Cu2O. Ketones don't react
37
What reagent is used in Tollens' Reagent?
Tollens' Reagent formed by mixing aqueous ammonia and silver nitrate.
38
What conditions are needed for Tollens' Reagent?
Heat gently
39
What reaction occurs in Tollens' Reagent?
Aldehydes only are oxidised by Tollens' reagent into a carboxylic acid. The silver (I) ions are reduced to silver atoms.
40
What is observed in Tollen's Reagent?
In aldehydes, a silver mirror forms coating the inside of the test tube. Ketones result in no visible change.
41
What is a biofuel?
A fuel produced from plants.
42
What is meant by carbon neutral?
An activity that has no net annual carbon emissions to the atmosphere.
43
What is an example of a biofuel?
Ethanol produced from fermentation.
44
Why is ethanol produced from fermentation known as carbon-neutral?
Because any carbon dioxide given off when the biofuel is burnt would have been extracted from the air by photosynthesis when the plant grew. Thus there would be no net CO2 emission into the atmosphere.
45
What are 3 equations that show no net contribution to CO2?
Photosynthesis Fermentation Combustion
46
Photosynthesis equation?
6H2O + 6CO2 -> C6H12O6 + 6O2
47
What do you understand from the photosynthesis equation regarding CO2?
6 Carbon Dioxide molecules are removed from the atmosphere when plants grow by photosynthesis to produce one molecule of glucose.
48
Fermentation equation?
C6H12O6 -> 2CH3CH2OH + 2CO2
49
Combustion equation?
2CH3CH2OH + 6O2 -> 4CO2 + 6H2O
50
What do you understand from the fermentation and combustion equation regarding CO2?
2 molecules of carbon dioxide are emitted from the fermentation of glucose. 4 more molecules of carbon dioxide are emitted in the combustion of ethanol. Thus 6 molecules of glucose are taken in during photosynthesis and then 6 are released during fermentation and combustion so it is a carbon neutral process.
51
What are the photosynthesis, combustion and fermentation reactions ignoring?
Any energy needed to irrigate plants, fractionally distil the ethanol from the reaction mixture or process the fuel. If the energy for these processes comes from fossil fuels then the ethanol produced is not carbon neutral.
52
What is a dehydrating reaction?
Removal of a water molecule from a molecule.
53
What is produced from the reaction of alcohols with dehydrating agents?
Alkenes
54
What reagent is needed for the reaction of alcohols with dehydrating agents?
Concentrated sulfuric acid or phosphoric acid.
55
What conditions are needed for the reaction of alcohols with dehydrating agents?
Warm under reflux
56
What is the role of the reagent (conc sulfuric acid or conc phosphoric acid)
Dehydrating agent/Catalyst
57
What type of reaction is the reaction of alcohols with dehydrating agents?
Acid catalysed elimination
58
What are the steps for the acid catalysed elimination mechanism?
1)Curly arrow from the lone pair on oxygen to the H+. 2)This forms a water molecule and O has a + charge now. 3)Curly arrow from the C-O bond to the O. 4)The water molecule breaks off and the carbon now has a + charge. 5)Curly arrow from the hydrogen to the C-C bond. 6)This forms an alkene and a H+.
59
What two ways can you form ethanol?
From ethene and from fermentation
60
What conditions are needed for fermentation?
Yeast No air Temperatures - 30-40 degrees celsius.
61
What is the optimum temperature for fermentation?
38 degrees celsius.
62
What happens at lower temperatures for fermentation?
Slow reaction
63
What happens at higher temperatures for fermentation?
The yeast dies and the enzymes denature.
64
Why is fermentation done in an absence of air?
Because the presence of air can cause extra reactions to occur.
65
What are 3 advantages of using fermentation to form ethanol?
Sugar (glucose) is a renewable resource Production uses low level technology Cheap equipment
66
What are 3 disadvantages of using fermentation to form ethanol?
Batch process so it is slow and gives high production costs. Ethanol made is not pure and needs to be purified by fractional distillation. Depletes land used for growing food crops.
67
What reagent is used for forming ethanol from ethene?
Ethene from cracking of fractions from distilled crude oil.
68
What type of reaction is the formation of ethanol from ethene?
Hydration/addition reaction.
69
Equation for forming ethanol from ethene?
CH2=CH2 (g) + H2O (g) -> CH3CH2OH (l)
70
What is hydration?
Addition of water to a molecule
71
What conditions are needed for the formation of ethanol from ethene?
High temperature (300 degrees celsius) High pressure (70 atm) Strong acidic catalyst of conc phosphoric acid.
72
3 Advantages of forming ethanol from ethene?
Faster reaction Purer product Continuous process - cheaper manpower.
73
3 Disadvantages of forming ethanol from ethene?
High tech equipment needed - expensive initial costs. Ethene is a non-renewable resource. High energy costs for pumping to produce high pressures.
74
Other than potassium dichromate solution, give one additional reagent that is needed to form any propanoic acid.
Sulfuric acid.
75
State the purpose of the small glass beads in an apparatus.
To prevent bumping.
76
State a simple chemical test that distinguishes an alcohol from a carboxylic acid. Give the observation for the alcohol and for the carboxylic acid.
Add sodium carbonate. Alcohol - No visible change. Carboxylic acid - Effervesence

Organic Chemistry (Year 1) (6 decks)

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