Chapter 15: Alcohols

Question 1

What is the C-O-H angle?

Answer 1

About 105 degrees because the 109.5 degrees angle of a perfect tetrahedron is brought down by the two lone pairs of electrons on the oxygen atom.

Question 2

Primary alcohol

Answer 2

OH
                  I
          R1 - C - H
                  I
                  H
-The carbon bonded to the -OH is bonded to 1 alkyl group and 2 hydrogen atoms.
-OH group is at the end of the chain.

Question 3

Secondary alcohol

Answer 3

OH
                  I
          R1 - C - R2
                  I
                  H
-The carbon bonded to the -OH is bonded to 2 alkyl groups and 1 hydrogen atom.
-OH group is in the body of the chain.

Question 4

Tertiary alcohol

Answer 4

OH
                  I
          R1 - C - R2
                  I
                  R3
-The carbon bonded to the -OH is bonded to 3 alkyl groups and 0 hydrogen atoms.
-OH group is at the branch of the chain.

Question 5

Why are the melting and boiling points of alcohols high?

Answer 5

Caused by the hydrogen bonding between the atoms, as it is the strongest type of IMF and therefore requires a lot of energy to overcome.

Question 6

What is the trend in solubility as the chain length of alcohols increases?

Answer 6

Trend: decreases
Explanation: the -OH group of alcohols can hydrogen bond to water molecules, but the non-polar hydrocarbon chain cannot. As the chain length increases, the non-polar area increases, leading to lower solubility.

Question 7

What is the equation for fermentation of glucose?

Answer 7

C6H12O6 (aq) -> 2C2H5OH (aq) + 2CO2 (g)

Question 8

What are the conditions needed for fermentation of glucose?

Answer 8

• carried out in solution (aq)
• relatively low temperatures (37 degrees Celsius)
• anaerobic conditions
• yeast

Question 9

What are the advantages of fermentation of glucose?

Answer 9

• low temperature and pressure, so low energy requirements.
• less use of fossil fuels because glucose comes from crops.
• carbon neutral process (number of moles of CO2 absorbed in photosynthesis = number of moles of CO2 released in fermentation and combustion)

Question 10

What are the disadvantages of fermentation of glucose?

Answer 10

• slower than hydration of ethene

- batch process

Question 11

What is the equation for hydration of ethene?

Answer 11

H2C=CH2 (g) + H20 (g) -> C2H5OH (l)

Question 12

What are the conditions needed for hydration of ethene?

Answer 12

• high temperatures (300 degrees Celsius)
• 60atm pressure
• H2O in the form of steam
• conc. phosphoric acid catalyst
• operated continously

Question 13

What are the advantages of hydration of ethene?

Answer 13

• relatively fast process
• continuous flow process
• produces pure ethanol

Question 14

What are the disadvantages of hydration of ethene?

Answer 14

• requires fairly high technology
• uses a lot of energy
• ethene comes from crude oil (non-renewable resource)