Methanol and the Home-Brewer

In June 2013, a young man in Queensland died as a result of drinking homemade liquor. It is believed that the liquor contained a toxic level of methanol (also known as wood alcohol). Drinking 10 mL of pure methanol can cause permanent blindness, drinking 30 mL of methanol can kill you.

The first step in the production of homemade liquors, is the fermentation of sugar.
Methanol, CH₃OH,is formed during fermentation.
When fermenting 6 kg of sugar dissolved in water for the production of distilled spirits such as whiskey or vodka, the home-brewer (and home-distiller) will typically find that the concentration of methanol in their brew is about 3 parts per million.

Many fruits are used by the home-brewer as the source of sugar to be fermented. Each fruit will lend a distinctive flavour to the final product. But fruits that are high in pectin will produce greater concentrations of methanol. Apples, apricots, guavas, quinces, plums, gooseberries, and citrus fruits like oranges, all contain high levels of pectin, typically more than 1% by mass pectin. Grapes, cherries and strawberries contain low levels of pectin, less than 1% by mass pectin.

Pectin contains  galacturonic acid which has the structural formula shown below:

In pectin, about 80% of the carboxyl groups in galacturonic acid are esterified with methanol. The remaining non-esterified carboxyl groups exist as the acid, or as salts with sodium, potassium or calcium. When pectin is broken down by enzymes during the brewing process, the methyl esters react with water to produce methanol.

The second step in the production of homemade liquor is the distillation step.
This is the crucial step in removing as much of the toxic methanol as possible.
The boiling point of methanol is about 65^oC, but the boiling point of ethanol (the desired product) is about 78^oC. During the distillation process, the first fraction collected should contain the methanol. This fraction should be collected and discarded. The next fraction should contain the desired liquor. It is highly recommended that any distillate collected after about 96^oC also be discarded.


Reference:
http://www.couriermail.com.au/news/queensland/ballandean-man-bill-lynam-who-lost-his-son-joel-to-homemade-liquor-poisoning-is-thankful-that-other-son-joshua-survived/story-fnihsrf2-1226664893229

Further Reading
http://ausetute.com.au/members/alkanolp.html (members only tutorial on alkanols)
http://ausetute.com.au/members/carboxyl.html (members only tutorial on alkanoic acids) 
http://ausetute.com.au/partspm.html 
http://ausetute.com.au/density.html 

Suggested Study Questions:

1. Draw the structural formula for methanol.
2. Locate the functional group present in methanol on the structural formula above. Name the functional group. 
3. At 25^oC methanol has a density of  0.79 g mL^-3. Calculate the mass of methanol present in a lethal dose of pure methanol .
4.  Convert the concentration of methanol given for homemade whiskey into a concentration in g mL^-1.
5. Assume the young man who died drank homemade whiskey. What minimum volume of homemade whiskey did he drink?
6. For galacturonic acid given the:
   • molecular formula
   • molar mass
7.  On the structural formula for galacturonic acid identify and name the functional groups present.
8. Draw the structure for the sodium salt of galacturonic acid.
9. Draw the structure for galacturonic acid esterified with methanol.
10. Give the molecular formula and molar mass for the structure above.
11. Apples contain about 1% by mass pectin. 10 kg of apples are to be used in the production of a homemade liquor. What mass of pectin will be present?
12. Assume exactly 100% of the carboxyl groups in galacturonic acid are esterified with methanol. How many moles of the ester are present in 10 kg of apples?
13. Write an equation representing the reaction between this ester and water to form methanol  and galacturonic acid.
14. How many moles of methanol could be produced by the break down of pectin in 10 kg of apples?
15. Assuming the young man who died had drunk this apple concoction without distilling and removing the methanol, what minimum volume of fermented apple-drink would he have had to have drunk?
16. Why do you think most countries have outlawed home-distilling?

Drunken Fruit Flies

Wasps are a major killer of fruit flies. They inject their eggs inside fruit fly larvae, then, when the wasp egg hatches, the wasp larva starts eating the fruit fly lava from the inside!
Scientists at Emory University have found that fruit flies prefer to lay their eggs in an environment  with a "high" concentration of ethanol. The fruit flies have evolved a certain amount of tolerance to this toxic ethanol, but the wasps who inject their eggs inside fruit fly larvae find the ethanol level to be lethal. Furthermore, fruit fly lava that have been infected with wasp larva tend to prefer to eat food with a high ethanol content, this raises their blood alcohol level and helps kill the wasp larva.

The most common natural source of ethanol is rotting fruit. Yeasts on rotting fruit can ferment the fruit sugars, like fructose, to produce ethanol:

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

This fermentation reaction takes place in anaerobic environments, that is, environments in which oxygen is not present.
The concentration of ethanol in rotting fruits has been  found to be between 0.04 and 0.72 v/v%. By comparison, the ethanol content in beer is usually between 3 and 6 v/v%, while the ethanol content of wine is between 8 and 11 v/v%.
Volume/volume (or volume) percent is a common way to refer to the concentration of alcoholic solutions. It refers to the volume of solute divided by the volume of solution which is then multiplied by 100, that is:

v/v% = V(solute)/V(solution) x 100

Beer that is 3 v/v% ethanol contains 3 mL of ethanol in every 100 mL of beer.

Wine that is 11 v/v% ethanol contains 11 mL of ethanol in every 100 mL of wine.

This preference for eating rotting fruit containing ethanol displayed by the fruit flies seems to be uncommon. Most animals, including humans, seem to prefer ripe, but not rotting, fruit.

References:

1. B. Z. Kacsoh, Z. R. Lynch, N. T. Mortimer, T. A. Schlenke. Fruit Flies Medicate Offspring After Seeing Parasites. Science, 2013; 339 (6122): 947 DOI: 10.1126/science.1229625
2. Neil F. Milan, Balint Z. Kacsoh, Todd A. Schlenke. Alcohol Consumption as Self-Medication against Blood-Borne Parasites in the Fruit Fly. Current Biology, 2012; 22 (6): 488 DOI: 10.1016/j.cub.2012.01.045

Further Reading:
Fermentation
Carbohydrates
Naming Alcohols
Density

Suggested Study Questions:

1. Calculate the volume of ethanol in a stubby (375 mL) of full strength beer (ethanol concentration 4.8 v/v%).
2. An average standard wine glass has a volume of 150 mL. What volume of ethanol is present in a standard wine glass of white wine with an ethanol concentration of 11.5 v/v%?
3. Port is an example of a fortified wine, that is, a wine that has had an additional distilled beverage like brandy added to it to increase its alcohol content to about 17.5 v/v%. A standard port glass has  a volume of 60 mL. Calculate the volume of ethanol in a standard glass of port.
4. The specific gravity (density) of ethanol is 0.789 g/mL. Calculate the mass of ethanol present in a stubby (375 mL) of
   • full strength beer (5 v/v% ethanol)
   • light beer (2.7 v/v% ethanol)
5. Spirits such as rum and vodka, have an ethanol concentration of approximately 40 v/v%. A standard "nip" is 30 mL. Calculate:
   • the volume of ethanol in a nip of vodka
   • the mass of ethanol in a nip of vodka
6. The alcohol content of Marsala wine is increased by allowing water to evaporate off it. The concentration of ethanol in Marsala wine will reach about 18 v/v%. Calculate:
   • volume of ethanol in a 750 mL bottle of Marsala
   • mass of ethanol in this bottle of Marsala wine
7. A particular type of wine barrel holds 225 L of wine. Calculate the mass of ethanol present if the wine in the barrel is
   • red wine (13 v/v% ethanol)
   • white wine (11.5 v/v% ethanol)
   • champagne (12 v/v% ethanol)

Hydronium Ions in Fermentation

Ethanol or ethyl alcohol (C₂H₅OH) can be produced from glucose (C₆H₁₂O₆) by fermentation using an enzyme as a catalyst:

C6H12O6

enzyme -------->

2 C2H5OH + 2 CO2

Chemists are very interested in studying this reaction because it has the potential to convert the sugars in woody biomass into alcohols which can be used as a fuel in place of non-renewable fuels obtained from petroleum. It is known that the enzyme in yeast which is commonly used in the production of ethanol loses its effectiveness when the pH of the reaction mixture is lowered.

In aqueous solutions, as soon as protons (H⁺) are released by an acidic species they bond with water molecules (H₂O) to form hydronium ions (H₃O⁺) :

H⁺ + H₂O → H₃O⁺

and pH is a measure of the hydronium ion concentration:
pH = -log[H₃O⁺]although we often think of this as being the same as a measure of the proton concentration:
pH = -log[H⁺]since we reasonably expect all the protons to have reacted with water molecules to form hydronium ions.

Los Alamos National Laboratory scientists substituted hydrogen in their enzyme samples with deuterium, an isotope of hydrogen (hydrogen-2). Unlike hydrogen-1 atoms, deuterium atoms provide a clear signal when bombarded with neutrons so they are visible to X-rays, this fact can be used to study the enzyme catalyzed process of fermentation.

The scientists found that as the pH fell below 6, hydronium ions (H₃O⁺) that are vitally important in the conversion of the sugar molecule into its fermentable form suddenly became dehydrated.
H₃O⁺ → H₂O + H⁺
The space in the enzyme occupied by the relatively large hydronium ion collapsed into a tiny volume occupied by the remaining proton (H⁺). This spatial change in the molecular structure prevented the sugar from being attacked by the enzyme.

The observed phenomenon provided an answer about why pH plays such an important role in the process and renders the enzyme inactive under acidic conditions. More important, it definitively illustrated that the hydronium ion plays a key role in the transport of protons in these types of biochemical systems.

Reference
Andrey Y. Kovalevsky, B. L. Hanson, S. A. Mason, T. Yoshida, S. Z. Fisher, M. Mustyakimov, V. T. Forsyth, M. P. Blakeley, D. A. Keen, Paul Langan. Identification of the Elusive Hydronium Ion Exchanging Roles with a Proton in an Enzyme at Lower pH Values. Angewandte Chemie International Edition, 2011; 50 (33): 7520 DOI: 10.1002/anie.201101753

Further Reading:
Mass-Mole Calculations
Gas Volume Calculations
Molarity Calculations
Yield Calculations
pH Calculations
Enzymes

Study Questions:

1. A Chemist undertook a fermentation experiment using 10g of glucose dissolved in 1L of water.
   • How many moles of glucose were present in the solution?
   • What was the concentration of the initial glucose solution?
   • What is the maximum yield of ethanol that could be produced from this reaction mixture?
   • If the actual yield of ethanol was 4% by mass, how many moles of ethanol was produced?
   • If the actual yield of ethanol was 4% by mass at 25^oC, what volume of carbon dioxide gas was be produced?
2. Assuming the fermentation of glucose reaction occurs at a constant temperature of 25^oC
   • Calculate the concentration of hydronium ions present in a reaction mixture with a pH of 6.
   • Calculate the concentration of hydroxide ions present in a solution with pH of 6
   • Calculate the pOH of a solution with a pH of 6.
3. What is meant by the term catalyst?
4. What is meant by the term enzyme?
5. Explain why the hydronium ion is larger than the hydrogen ion.
6. Would the hydronium ion be larger or smaller than a water molecule? Explain your answer.
7. How would you define the term isotope?
8. Explain why deuterium is considered to be an isotope of hydrogen.
   
   
   

Butanol Biofuel

A team of chemical engineers at the University of Arkansas has developed a method for converting common algae into butanol, a renewable fuel that can be used in existing combustion engines.

Butanol has several significant advantages over ethanol, the current primary additive in petrol (gasoline). Butanol releases more energy per unit mass and can be mixed in higher concentrations than ethanol. It is less corrosive than ethanol and can be shipped through existing pipelines. These attributes are in addition to the advantages gleaned from butanol's source. Unlike corn, algae are not in demand by the food industry. Furthermore, it can be grown virtually anywhere and thus does not require large tracts of valuable farmland.

The team grows algae on "raceways," which are long troughs made out of screens or carpet, usually 2 feet wide and ranging from 5-feet to 80-feet long, depending on the scale of the operation. Algae survive on nitrogen, phosphorus, carbon dioxide and natural sunlight, so the researchers grow algae by running nitrogen- and phosphorus-rich creek water over the surface of the troughs. Excess nitrogen and phosphorus in natural waters is sometimes referred to as "dead zones" because these elements in excess can kill fish and plants.
They enhance this algal growth by delivering high concentrations of carbon dioxide through hollow fiber membranes that look like long strands of spaghetti.

The researchers harvest the algae every five to eight days by vacuuming or scraping it off the screens. After waiting for it to dry, they crush and grind the algae into a fine powder as the means to extract carbohydrates from the plant cells. Carbohydrates are made of sugars and starches. They treat the carbohydrates with acid and then heat them to break apart the starches and convert them into simple, natural sugars. They then begin a unique, two-step fermentation process in which organisms turn the sugars into the organic acids butanoic acid( butyric acid), lactic acid and ethanoic acid (acetic acid).

The second stage of the fermentation process focuses on butanoic acid (butyric acid) and its conversion into butanol. The researchers use a unique process called electrodeionization which involves the use of a special membrane that rapidly and efficiently separates the acids during the application of electrical charges.

Reference:
University of Arkansas, Fayetteville (2011, March 2). Algae converted to butanol; Fuel can be used in automobiles. ScienceDaily. Retrieved March 11, 2011, from http://www.sciencedaily.com­ /releases/2011/03/110301200638.htm

Further Reading
Elements and Compounds
Nomenclature
Alkanols (alcohols)
Functional Groups
Carbohydrates
Carbon Cycle


Study Questions

1. Draw a table with the headings elements and compounds. Place each element and compound mentioned in the article above into the table.
2. Give the formula for each of the following:
   
   • butanol
   • ethanol
   • nitrogen gas
   • carbon dioxide gas
   • butanoic acid
3. Describe what is meant when a Chemist uses the term carbohydrate.
4. What is the difference between a sugar and a starch?
   
5. Give 3 examples of compounds that are carbohydrates.
6. Write an equation to represent the process by which algae produce glucose from carbon dioxide and water.
   
7. Write an equation to represent the fermentation of glucose into ethanol.
8. What are the advantages of using butanol as an additive to petrol (gasoline) rather than ethanol?