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chemistry a level > Alcohols, Haloalkanes and Analysis > Flashcards

Alcohols, Haloalkanes and Analysis Flashcards

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1
Q

What is a primary alcohol?

A

An alcohol where the carbon attached to the hydroxyl group is only attached to one other carbon

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2
Q

What is a secondary alcohol?

A

An alcohol where the carbon attached to the hydroxyl group is attached to two other carbons

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3
Q

What is a tertiary alcohol?

A

An alcohol where the carbon that is attached to the hydroxyl group is attached to 3 other carbons

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4
Q

Why are short chained alcohol molecules soluble in water?

A

The OH group forms hydrogen bonds with the water molecules, this enables dissolve in water. Larger alcohol molecules aren’t soluble in water as the alkyl chain becomes too long and disrupts the hydrogen bonding of the OH group with the water molecules

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5
Q

What are the products of complete combustion?

A

Carbon dioxide and water

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6
Q

What are the products of incomplete combustion

A

Carbon monoxide and water

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7
Q

Which alcohols can be oxidised by an oxidising agent?

A

Primary and secondary alcohols

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8
Q

What does the oxidisation of a primary alcohol produce?

A

An aldehyde and then a carboxylic acid, partial oxidation produces an aldehyde, reflux produces a carboxylic acid

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9
Q

What does the oxidisation of a secondary alcohol produce?

A

A ketone, heat under reflux

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10
Q

What is the oxidising agent used to oxidise primary and secondary alcohols?

A

Acidified potassium dichromate, K2Cr2O7 / H+

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11
Q

Describe the process of reflux

A
  • Add the pre weighed potassium dichromate to a pear shaped flask using a funnel
  • Slowly add 20cm^3 of 3.0 moldm-3 sulfuric acid to the pear shaped flask using a funnel
  • Add a few anti-bumping granules (to make the mixture boil more calmly) and swirl the flask to dissolve the solid
  • Cool the solution by swirling the flask in an ice water bath for 2-3 minutes until the solution is cooler than 10 degrees
  • Carefully add 0.5cm^3 of ethanol to the flask drop wise while swirling the flask in ice water
  • Continue to swirl the mixture in ice water and monitor the temperature of the reaction with a thermometer
  • Clamp the flask by the neck, position in your heating apparatus and arrange the condenser above the flask in a reflux setup, turn on the condenser water flow
  • Heat the reaction mixture under reflux for around 20 minutes
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12
Q

Write the equation of the oxidation of propan-1-ol to propanal

A

C3H7OH + [O] → CH3H6O + H2O

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13
Q

Write the equation of the oxidation of propan-1-ol to propanoic acid

A

CH3H7OH + 2[O] →CH2H5COOH + H2O

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14
Q

Write the equation of the oxidation of a butan-2-ol to butanone

A

C4H9OH + [O] →CH3COC2H5 + H2O

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15
Q

What is the observation in the oxidation of any class of alcohol?

A

Colour change from orange to green

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16
Q

What is the trend in reactivity of haloalkanes?

A
  • Going down the halogen group the reactivity of the haloalkanes increases, with fluoroalkanes being the least reactive and iodoalkanes being the most reactive
  • As you go down the halogen group, the atomic radius increases in size and therefore their bonding electrons experience a greater shielding effect and a weaker nuclear attraction, this means bonds that these electrons form have lower bond enthalpies than bonds formed by bonding electrons of elements further up the group
  • The lower bond enthalpy means that the C-X bond is easier to break and therefore the haloalkanes of elements further down the group are more reactive
17
Q

What is the order of reactivity of the haloalkanes?

A

Most reactive- Iodoalkanes, bromoalkanes, chloroalkanes, fluoroalkanes -Least reactive

18
Q

Will there be a faster rate of hydrolysis using water or an aqueous alkali such as NaOH?

A

An aqueous alkali as it fully dissociates meaning it releases more OH- ions at a faster rate than water

19
Q

Write the mechanism for the decomposition of ozone by chlorine radicals

A

Propagation- Cl. + O3 → ClO. + O2
- ClO. + O3 → Cl. + 2O2
Overall- 2O3 → 3O2

20
Q

Write the mechanism for the decomposition of ozone by NO radicals

A

NO. + O3 → NO2. + O2
NO2. + O → NO. + O2
Overall- O3 + O → 2O2

21
Q

What is the molecular formula of a typical CFC?

A

C2F2Cl2

22
Q

Does potassium dichromate change colour at low temperatures when added to a ketone?

A

No, tit will only react with aldehydes at low temperatures, this is a way to determine what product you have formed

23
Q

What is the half equation for the reduction of Cr2O7^2-?

A

Cr2O7^2- + 14H+ + 6e- → 2Cr3+ + 7H2O

24
Q

What is the half equation for the oxidation of an aldehyde?

A

3RCHO + 3H2O → 3RCOOH + 6H+ + 6e-

25
Q

What is the overall equation for the oxidation of an aldehyde?

A
  • 3RCHO + Cr2O7^2- + 8H+ → 2Cr3+ + 3RCOOH + 4H2O

- Or simplified: RCHO + [O] → RCOOH

chemistry a level (15 decks)

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