C14 Alcohols Flashcards

1
Q

Physical properties of alcohols compared to alkanes

A

Less volatile

Higher MPs

Greater H2O solubility

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2
Q

Reason for physical properties of alkanes

A

Non-polar bonds as EN of C + H very similar

IMFs between non-polar molecules are very weak LFs

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3
Q

Reason for physical properties of alcohols

A

Polar O-H bonds (diff in EN of O and H atoms)

IMFs are very weak LFs but theres also strong HBs between polar O-H

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4
Q

Why do alcohols have higher BPs and lower volatility than alkanes

A

HBs require more energy to break than weaker LFs in alkanes

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5
Q

Solubility of alkanes in water

A

Non-polar

Cannot form HBs with H2O

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6
Q

Solubility of alcohols in water

A

Completely soluble in water

HBs form between polar -OH groups of alcohol + H2O

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7
Q

What happens to solubility as chain length increases

A

C chain length increases

Influence of -OH becomes smaller

Solubility decreases

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8
Q

What is the colour change when alcohols are oxidised

A

Orange to green

Dichromate (VI) ions reduced to chromium (III) ions

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9
Q

What do primary alcohols oxidise to

A

Aldehyde or carboxylic acid

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10
Q

Oxidation of primary alcohol to form aldehyde

A

Gentle heating

K2Cr2O7/H2SO4

Aldehyde distilled out as it forms

Colour change : orange to green

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11
Q

Oxidation of primary alcohol to form carboxylic acid

A

Reflux

Excess K2Cr2O7/H2SO4

Orange to green

Form carboxylic acid + water

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12
Q

What does oxidising secondary alcohols produce

A

Ketones

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13
Q

Oxidising tertiary alcohols

A

Don’t undergo oxidation reactions

Oxidation mixture remains orange

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14
Q

Oxidising secondary alcohol to produce ketone

A

Reflux

K2Cr2O7/H2SO4

Orange to green

Produce ketone + water

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15
Q

Word equation of complete combustion of alcohol

A

Alcohol + O2 —> CO2 + H2O

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16
Q

what type of reaction is combustion?

A

exothermic reaction as it releases a large amount of energy in the form of heat.

17
Q

what conditions are needed for an alcohol to undergo a substitution reaction with a hydrogen halide?

A

hydrogen halide

reflux

sulfuric acid

sodium halide

forms haloalkane

18
Q

what is a dehydration reaction?

A

any reaction in which a water molecule is removed from the starting material

19
Q

What’s the general formula of an alcohol

A

CnH2n+1 OH

20
Q

What kind of IMFs do alcohols have and why

A

Hydrogen bonding

Due to electronegativity difference in OH bond

21
Q

Hoe do alcohols MP and BP compare to other hydrocarbons’ of similar C chain lengths? Why?

A

Higher, because they have HB (strongest type of IMF) —> stronger than LFs

22
Q

Are alcohols soluble in water? Why does solubility depend on chain length?

A

Soluble when short chain - OH HBs to HB in water

Insoluble when long chain - non-polarity of C-H bond takes precedence

23
Q

What forms if you partially oxidise a primary alcohol

A

An aldehyde

24
Q

What conditions are needed to partially oxidise a primary alcohol

A

Dilute H2SO4, potassium dichromate (VI), distill product as its produced, gentle heating

25
What conditions are needed to fully oxidise a primary alcohol
Conc H2SO4, potassium dichromate (VI), reflux, strong heating
26
What forms if you oxidise a secondary alcohol
A ketone
27
What conditions are needed for the oxidation of a secondary alcohol
Conc H2SO4, potassium dichromate (VI), strong heating
28
What are the products of dehydration reaction of alcohol
Alkene and water
29
What are the conditions required for dehydration of alcohol
Conc H2SO4 or conc H3PO4 and 170*C
30
What are the products of the halide substitution reaction with alcohol
Haloalkane and water
31
In what form is the halide used in halide substitution reaction
In the form of hydrogen halide, e.g. HBr
32
How is hydrogen halide made in situ? Give examples
A salt is reacted with acid to form the hydrogen halide E.g. sodium bromide reacts with sulfuric acid to form HBr When iodine is reacted phosphoric acid is used as sulfuric acid oxidises iodide ions into iodide