Ethanol From Sucrose 1. Give a two-step equation for fermentation, using structu

Question

Ethanol From Sucrose

1. Give a two-step equation for fermentation, using structural formulas for the reactants and intermediate products.

2. Condense your answer to Question 1 into a balanced, one-step equation, using only the chemical formulas and omitting intermediate products.

3. What temperature should not be exceeded? Why?

4. a) What side products cause hangover headaches? b) Draw their structures.

5. a) From what organic compound is industrial ethanol now made? b) Write a reaction for this process.

6. a) What is the percentage range of maximum ethanol production in fermentation? b) Why would reaching equilibrium not be the reason fermentation stops? Hint – where does the carbon dioxide go when it is formed? c) Why do you think fermentation stops? Hint- consider the effect of the product on the catalyst.

7. If air had not been excluded from the fermentation, the alcohol product could have been oxidized first to a two carbon compound then a one carbon compound. Give the formulas.

8. Refer to the diagram below: a) What is the approximate boiling point of a mixture that is 10% ethanol? b) What is the approximate composition of the vapor that escapes? c) When that vapor condenses, what is the approximate boiling point of the liquid it becomes? d) When that liquid boils, what is the approximate composition of the vapor that escapes? e) How do the composition and boiling point of the distillate change as it rises in the column? What do they eventually become? f) Can fractional distillation separate a mixture that is 95.6% ethanol? If so, how? If not, why not?

Explanation / Answer

1.Sucrose is a dimer of glucose and fructose molecules. In the first step of alcoholic fermentation, the enzyme invertase cleaves the glycosidic linkage between the glucose and fructose molecules.

C12H22O11+ H2O + invertase 2 C6H12O6

Next, each glucose molecule is broken down into two pyruvate molecules in a process known as glycolysis.Glycolysis is summarized by the equation

C6H12O6+ 2 ADP + 2 Pi+ 2 NAD+ 2 CH3COCOO+ 2 ATP + 2 NADH + 2 H 2O + 2 H+

pyruvate is CH3COCOO. Pi stands for the inorganic phosphate.

2. The overall chemical formula for alcoholic fermentation is:

C6H12O6 2 C 2H5OH + 2 CO2

3.Temperature should not exceed 27°c as yeast killed above this.

4.several factors are known to be involved including acetaldehyde accumulation,glucosemetabolism,dehydration,, Beverage-specific effects of additives or by-products such as congeners in alcoholic beverages

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