Alcohols

State and explain the bond angel of H-C-H and C-C-O in an alcohol (3)

• 109.5

• 4 bonding pairs of electrons

• Repelling to a position of minimum repelling

State and explain the bond angle in H-O-C in an alcohol (4)

• 104.5

• 2 bonding pairs and 2 lone pairs

• Repelling to a position of minimum repulsion

• Lone pairs repel more than bonding pairs so angle is reduced

Explain the boiling points of alcohols

• High

• Due to relatively low volatility

• And ability to form hydrogen bonds between alcohol molecules

What are the conditions for the partial oxidation of primary alcohols (2)

• Reagent : potassium dichromate (VI) and dilute sulphuric acid

• Conditions : warm and distil aldehyde as if forms

What is the reaction in the partial oxidation of primary alcohols (1)

Primary alcohol to aldehyde and water molecule

What is the reaction for the full oxidation of primary alcohols (1)

Primary alcohol to carboxylate acid and water molecule

What are the conditions for the full oxidation of primary alcohols (2)

• Reagant: potassium dichromate (VI) and dilute sulfuric acid

• Conditions ; heat under reflux

What is the reaction of the oxidation of secondary alcohols

Secondary alcohol to ketone and water molecule

What are the conditions for the oxidation of secondary alcohols (2)

• Reagent : potassium dichromate (VI) and diluted sulfuric acid Conditions

• Conditions: heat under reflux

Why can’t tertiary alcohols be oxidised (1)

There is no hydrogen atom bonded to the carbon with the -OH group

Explain the process for testing for aldehydes using tollens Reagant (5)

• Form tollens reagent by mixing aqueous ammonia and silver nitrate

• Heat gently

• Aldehydes are oxidised into carbolxylic acid

• And silver ions are reduced to silver atoms

• Forming a silver mirror coat

What is the chemical formula for tollens reagent (1)

[Ag(NH3)2]+

Explain the process for testing for aldehydes using Fehlings solution (4)

• Heat gently

• Aldehydes are oxidised into carboxylic acid

• Copper (II) ions are reduced to copper (I) oxide

• which produces a colour change from blue to red

How can you test for the presence of a carboxylic acid (2)

• Add sodium carbonate

• It will fizz and produce carbon dioxide

What are the conditions for converting an alcohol into an alkene

• Reagant : conc sufuric acid

• Conditions : warm under reflux

What is a dehydration reaction (1)

Removes a water molecule from a molecule

What type of reaction if the conversion of alcohol to alkene (1)

Acid catalysed elimination

Draw out the displayed formulas for the reaction of converting an alcohol into an alkene

Draw out the acid catalysed elimination mechanism to form alkene from alcohol

What is the word equation for the fermentation of glucose (2)

Glucose to ethanol and carbon dioxide

What is the chemical equation for the fermentation of glucose (3)

What are the conditions needed for fermentation of glucose (3)

• Yeast

• No air

• 38 degrees Celsius

Why is 38 the temperature used for fermentation (2)

• At lower, the reaction is too slow

• At higher, the yeast dies and enzymes denature

Why is fermentation done in the absence of air (1)

Because air can oxidise the ethanol to ethanol acid

What are the advantages of fermentation (3)

• Sugar is renewable resource

• Production uses low technology

• Production uses cheap equipment

What are the disadvantages of fermentation (3)

• Batch process is slow and gives high production costs

• Ethanol made is not pure and needed purification by fractional distillation

• Depletes land is used for growing food crops

Explain the conditions required to form ethanol from ethene (3)

• 300 c

• 70 atm

• H3PO4

What are the advantages of producing ethanol from ethene (3)

• Faster reaction

• Purer product

• Continuous process

What are the disadvantages of producing ethanol from ethene (3)

• High tech equipment costs

• Ethene is non renewable resource

• High energy costs to produce high pressures

Draw the mechanism for the hydration of ethene to form ethanol

What does the term carbon neutral mean (1)

An activity that has no net annual carbon emissions to the atmosphere

Write out the equations that show no net contribution to CO2 through photosynthesis and fermentation (4)

What is the mechanism for the greenhouse effect (6)

• UV wavelength radiation passes through the atmosphere to earth surface

• and heats up earths surface

• Earth radiates our infrared long wavelength radiation

• C=O bonds in carbon dioxide absorb infrared radiation so the IR radiation does not escape from atmosphere

• This energy is transferred to other molecules in atmosphere by collision

• Therefore atmosphere is warmed

How can you test for primary and secondary alcohol (2)

• Add potassium dichromate and sulfuric acid

• Colour change from orange to green