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Biological Sciences Foundation Year > Alcohol > Flashcards

Alcohol Flashcards

1
Q

Define the general formula for alcohols.

A

The general formula for alcohols is CnH2n+1OH.

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2
Q

Describe the naming convention for alcohols.

A

Alcohols are named with the ending -ol, and if necessary, the position number for the OH group is added between the name stem and -ol.

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3
Q

How are alcohols with multiple -OH groups named?

A

Alcohols with two or more -OH groups use the prefixes di or tri, and the ‘e’ is added to the stem name, such as ethan-1,2-diol or propan-1,2,3-triol.

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4
Q

Differentiate between primary, secondary, and tertiary alcohols.

A

Primary alcohols have 1 carbon attached to the carbon adjoining the oxygen, secondary alcohols have 2 carbons, and tertiary alcohols have 3 carbons attached.

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5
Q

What is the bond angle in primary and secondary alcohols?

A

The bond angle in primary and secondary alcohols is 109.5 degrees due to the tetrahedral shape.

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6
Q

Explain the bond angle in the H-O-C bond of alcohols.

A

The bond angle in the H-O-C bond is 104.5 degrees because there are 2 bonding pairs and 2 lone pairs of electrons, leading to a bent line shape.

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7
Q

How do hydrogen bonds affect the properties of alcohols?

A

Hydrogen bonds between alcohol molecules result in relatively low volatility and high boiling points.

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8
Q

What allows smaller alcohols to dissolve in water?

A

Smaller alcohols can dissolve in water because they can form hydrogen bonds with water molecules.

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9
Q

Identify the structural formula for butan-2-ol.

A

The structural formula for butan-2-ol is CH3-CH(OH)-CH2-CH3.

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10
Q

What prefix is used for an alcohol with two -OH groups?

A

The prefix used for an alcohol with two -OH groups is ‘di’.

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11
Q

How does the presence of lone pairs affect bond angles in alcohols?

A

Lone pairs repel more than bonding pairs, which reduces the bond angle in alcohols.

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12
Q

What is the significance of the -ol suffix in alcohol nomenclature?

A

The -ol suffix indicates that the compound is an alcohol, specifically containing an -OH group.

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13
Q

Describe the shape of the alcohol molecule based on its bonding pairs.

A

The shape of the alcohol molecule is tetrahedral due to four bonding pairs of electrons around the carbon atoms.

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14
Q

What is the effect of hydrogen bonding on the boiling points of alcohols?

A

Hydrogen bonding leads to higher boiling points in alcohols compared to similar-sized hydrocarbons.

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15
Q

Describe the role of potassium dichromate in the oxidation of alcohols.

A

Potassium dichromate (K2Cr2O7) acts as an oxidising agent that facilitates the oxidation of alcohols, converting them into aldehydes or ketones depending on the type of alcohol.

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16
Q

Define the outcome of the partial oxidation of primary alcohols.

A

The partial oxidation of primary alcohols results in the formation of aldehydes.

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17
Q

How does the oxidation of primary alcohols occur in terms of reagents and conditions?

A

The oxidation occurs using potassium dichromate (VI) solution and dilute sulfuric acid under gentle warming with a limited amount of dichromate, while distilling out the aldehyde as forms.

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18
Q

What is the significance of the C=O bond in aldehydes?

A

The C=O bond in aldehydes is always located on the first carbon of the chain, which means aldehydes do not require a number in their name.

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19
Q

Explain the observation made during the oxidation of alcohols with potassium dichromate.

A

During the oxidation, the orange dichromate ion (Cr2O7^2-) reduces to the green Cr^3+ ion.

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20
Q

How should oxidation equations be simplified when representing the oxidation of alcohols?

A

Oxidation equations can be simplified using

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21
Q

Describe the process of distillation in the context of organic chemistry.

A

Distillation is a separation technique used to isolate an organic product from its reacting mixture by collecting the distillate at the approximate boiling point of the desired product.

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22
Q

What is the purpose of the thermometer in a distillation setup?

A

The thermometer measures the boiling point of the distillate, and its bulb should be positioned at the T junction connecting to the condenser for accurate readings.

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23
Q

How does the design of the Liebig condenser enhance its efficiency?

A

The Liebig condenser is designed to have water enter from the bottom, which goes against gravity, allowing for more efficient cooling and preventing backflow of water.

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24
Q

Why are electric heaters preferred for heating organic chemicals?

A

Electric heaters are preferred because organic chemicals are highly flammable and could ignite if exposed to an open flame.

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25
Q

What can be done to improve the yield of distillate during distillation?

A

Cooling the collection flask in ice can help improve the yield of distillate during distillation.

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26
Q

Describe the full oxidation process of primary alcohols.

A

Primary alcohols are oxidized to carboxylic acids using potassium dichromate(VI) solution and dilute sulfuric acid under reflux conditions.

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27
Q

What reagent is used for the oxidation of primary alcohols?

A

Potassium dichromate(VI) solution and dilute sulfuric acid are used as reagents for the oxidation of primary alcohols.

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28
Q

Define the conditions necessary for oxidizing primary alcohols.

A

An excess of potassium dichromate is required, and the reaction must be heated under reflux.

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29
Q

How does the observation change during the oxidation of primary alcohols?

A

The orange dichromate ion (Cr2O7^2-) reduces to the green Cr^3+ ion during the oxidation process.

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30
Q

What is the purpose of reflux in organic reactions?

A

Reflux is used to heat organic reaction mixtures for long periods while preventing organic vapors from escaping.

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31
Q

Explain the function of the condenser in a reflux setup.

A

The condenser cools and condenses organic vapors back into liquids, preventing them from escaping the reaction mixture.

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32
Q

What safety precaution should be taken regarding the condenser during reflux?

A

The end of the condenser should never be sealed to avoid the build-up of gas pressure, which could cause an explosion.

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33
Q

What are anti-bumping granules used for in distillation and reflux?

A

Anti-bumping granules are added to prevent vigorous, uneven boiling by promoting the formation of small bubbles instead of large ones.

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34
Q

How should the apparatus for reflux be accurately drawn and labeled?

A

The drawing should not include lines between the flask and condenser, the top of the condenser should not be sealed, and the condenser must have an outer tube for water that is sealed at both ends.

35
Q

What is the chemical equation for the oxidation of propan-1-ol to propanoic acid?

A

The equation is CH3CH2CH2OH + 2[O] → CH3CH2COOH + H2O.

36
Q

What happens to the dichromate ion during the oxidation of primary alcohols?

A

The dichromate ion (Cr2O7^2-) is reduced to the green Cr^3+ ion.

37
Q

What is the role of water in the reflux process?

A

Water circulates through the condenser to remove heat and condense vapors back into liquid.

38
Q

Identify the product formed from the oxidation of propan-1-ol.

A

The product formed is propanoic acid.

39
Q

Describe the reaction that occurs when secondary alcohols are oxidized.

A

Secondary alcohols are oxidized to ketones using potassium dichromate(VI) solution and dilute sulfuric acid under heat and reflux.

40
Q

Define the product formed from the oxidation of secondary alcohols.

A

The product formed is a ketone.

41
Q

How do you name ketones with five or more carbon atoms in the chain?

A

Ketones with five or more carbon atoms require a number to indicate the position of the double bond, e.g., pentan-2-one.

42
Q

What is the observation when potassium dichromate is used to oxidize secondary alcohols?

A

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

43
Q

Explain why tertiary alcohols cannot be oxidized by potassium dichromate.

A

Tertiary alcohols cannot be oxidized because there is no hydrogen atom bonded to the carbon with the -OH group.

44
Q

Distinguish between aldehydes and ketones based on their oxidation behavior.

A

Aldehydes can be further oxidized to carboxylic acids, whereas ketones cannot be further oxidized.

45
Q

What is Tollens’ reagent and how is it prepared?

A

Tollens’ reagent is prepared by mixing aqueous ammonia and silver nitrate, resulting in the complex ion [Ag(NH3)2]+.

46
Q

What happens when aldehydes are treated with Tollens’ reagent?

A

Aldehydes are oxidized to carboxylic acids, and silver(I) ions are reduced to silver atoms, forming a silver mirror.

47
Q

What is the observation when aldehydes react with Tollens’ reagent?

A

A silver mirror forms, coating the inside of the test tube.

48
Q

Describe the reaction of aldehydes with Fehling’s solution.

A

Aldehydes are oxidized to carboxylic acids, and the blue Cu^2+ ions are reduced to a red precipitate of Cu2O.

49
Q

What is the observation when aldehydes are mixed with Fehling’s solution?

A

The blue Cu^2+ ions change to a red precipitate of Cu2O.

50
Q

How can the presence of a carboxylic acid be tested?

A

The presence of a carboxylic acid can be tested by adding sodium carbonate, which will fizz and produce carbon dioxide.

51
Q

Describe the dehydration reaction of alcohols.

A

The dehydration reaction involves the removal of a water molecule from an alcohol, resulting in the formation of an alkene.

52
Q

Identify the reagents used in the dehydration of alcohols.

A

Concentrated sulfuric acid or phosphoric acid are used as reagents in the dehydration of alcohols.

53
Q

What conditions are required for the dehydration reaction of alcohols?

A

The dehydration reaction requires warm conditions, typically under reflux.

54
Q

Define the role of the reagent in the dehydration reaction of alcohols.

A

The reagent acts as a dehydrating agent and catalyst in the reaction.

55
Q

Explain the type of reaction that occurs during the dehydration of alcohols.

A

The dehydration of alcohols is classified as an acid-catalyzed elimination reaction.

56
Q

How can secondary and tertiary alcohols differ in their dehydration products?

A

Secondary and tertiary alcohols can yield more than one product due to the formation of double bonds between different carbon atoms.

57
Q

What are the possible products of butan-2-ol when dehydrated?

A

Butan-2-ol can form both but-1-ene and but-2-ene, with but-2-ene being the major product.

58
Q

Describe the isomerism that can occur with but-2-ene.

A

But-2-ene can exist as E and Z isomers due to the different spatial arrangements of the substituents around the double bond.

59
Q

How does producing alkenes from alcohols benefit polymer production?

A

Producing alkenes from alcohols provides a route to polymers without relying on monomers derived from oil.

60
Q

Illustrate the dehydration reaction of propan-1-ol.

A

The reaction of propan-1-ol results in the formation of propene and water: CH3CH2CH2OH → CH2=CHCH3 + H2O.

61
Q

What is the source of the H+ ion in the acid-catalyzed elimination mechanism?

A

The H+ ion comes from concentrated sulfuric acid (H2SO4) or concentrated phosphoric acid (H3PO4).

62
Q

Describe the process of fermentation for producing ethanol.

A

Fermentation involves converting glucose into ethanol and carbon dioxide using yeast in the absence of air, typically at temperatures between 30 to 40 °C, with an optimum around 38 °C.

63
Q

What are the essential conditions for fermentation to occur?

A

The essential conditions for fermentation include the presence of yeast, absence of air, and temperatures between 30 to 40 °C.

64
Q

Define the chemical equation for fermentation.

A

The chemical equation for fermentation is C6H12O6 → 2 CH3CH2OH + 2 CO2.

65
Q

How does the presence of air affect the fermentation process?

A

The presence of air can lead to the oxidation of ethanol to ethanoic acid (vinegar), which is undesirable for ethanol production.

66
Q

List the advantages of using fermentation to produce ethanol.

A

Advantages of fermentation include the use of sugar as a renewable resource and the requirement for low-level technology and cheap equipment.

67
Q

What are the disadvantages of fermentation in ethanol production?

A

Disadvantages of fermentation include being a slow batch process with high production costs, producing impure ethanol that requires purification, and depleting land used for food crops.

68
Q

Describe the industrial method of producing ethanol from ethene.

A

The industrial method involves the hydration of ethene, where ethene reacts with water under high temperature (300 °C) and high pressure (70 atm) in the presence of a strong acidic catalyst, typically concentrated H3PO4.

69
Q

What are the advantages of producing ethanol from ethene?

A

Advantages include a faster reaction, a purer product, and a continuous process that reduces manpower costs.

70
Q

Identify the disadvantages of producing ethanol from ethene.

A

Disadvantages include the need for high technology equipment, the non-renewable nature of ethene, and high energy costs associated with maintaining high pressures.

71
Q

Define hydration in the context of ethanol production.

A

Hydration is the addition of water to a molecule, specifically in the context of ethene reacting with water to form ethanol.

72
Q

What type of reaction is fermentation classified as?

A

Fermentation is classified as a type of reaction that involves the conversion of sugars into alcohol and carbon dioxide.

73
Q

What type of reaction is the hydration of ethene classified as?

A

The hydration of ethene is classified as an addition reaction.

74
Q

Explain the role of the acidic catalyst in the hydration of ethene.

A

The acidic catalyst, typically concentrated H3PO4, facilitates the addition of water to ethene, allowing the reaction to proceed under the required high temperature and pressure.

75
Q

Define biofuel.

A

A biofuel is a fuel produced from plants.

76
Q

Describe the process of ethanol production from fermentation.

A

Ethanol is produced from the fermentation of glucose, which is derived from plants.

77
Q

How is ethanol considered carbon-neutral?

A

Ethanol is considered carbon-neutral because the carbon dioxide released when it is burned is offset by the carbon dioxide absorbed by plants during photosynthesis.

78
Q

What factors can affect the carbon neutrality of ethanol production?

A

The carbon neutrality of ethanol production can be affected by the energy used for irrigation, distillation, and processing, especially if that energy comes from fossil fuels.

79
Q

Explain the photosynthesis equation related to carbon dioxide removal.

A

The equation for photosynthesis is 6 CO2 + 6 H2O → C6H12O6 + 6 O2, which shows that plants absorb carbon dioxide to produce glucose and oxygen.

80
Q

What is the fermentation equation for glucose?

A

The fermentation of glucose is represented by the equation C6H12O6 → 2 CH3CH2OH + 2 CO2.

81
Q

Describe the combustion process of ethanol.

A

The combustion of ethanol can be represented by the equation 2 CH3CH2OH + 6 O2 → 4 CO2 + 6 H2O, which produces carbon dioxide and water.

82
Q

Summarize the overall carbon dioxide balance in ethanol production.

A

For every 6 molecules of CO2 absorbed by plants, 6 molecules of CO2 are emitted during fermentation and combustion, resulting in no net contribution to atmospheric CO2.

83
Q

What does the term ‘carbon neutral’ mean?

A

Carbon neutral refers to an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere.

Biological Sciences Foundation Year (17 decks)

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