Alkanol + HX

What happens when you add a concentrated hydrohalic acid, like hydrobromic acid or hydrochloric acid or hydroiodic acid, to an alkanol?
A substitution reaction!
Find out more in AUS-e-TUTE's new tutorial at https://www.ausetute.com.au/alkanolhx.html

AUS-e-TUTE Members should log-in to use the new tutorial, game and test (with worked solutions!).

Blood Alcohol Concentration

Drinking alcohol impairs your driving ability, so legal limits are set, not for the amount of alcohol you consume, but on the effects of alcohol in your system. In Australia we measure the amount of alcohol in your blood (BAC or Blood Alcohol Concentration) and have set a "maximum legal limit" of 0.05% for most drivers (BAC for learner, provisional and professional drivers is less).
A Blood Alcohol Concentration, BAC, of 0.05% is a weight per volume percentage, w/v%, that is, a BAC of 0.05% is 0.05 grams of alcohol in every 100 mL of blood.
Your Blood Alcohol Concentration, BAC, is effected by the alcoholic beverages you consume. The concentration of alcohol varies between different types of alcoholic beverages, and is given as w/v% concentration as shown in the table below:

Alcoholic Beverage	Typical Alcohol Concentration
light beer	2.7%
ordinary beer	4.9%
wine	12%
spirits	40%
port or sherry	20%

So drinking 100 mL of wine will increase your blood alcohol concentration more than drinking 100 mL of beer.

But drinking alcoholic beverages is not the only way that alcohol can enter your blood stream. Alcohol is also present as an ingredient in other things you might ingest such as in some mouthwashes where it is used for its anti-bacterial properties, for example, original formula Listerine mouthwash contains 26.9% alcohol. Alcohol is also found as the solvent in many over-the-counter and prescription medications, for example, Benedryl has an alcohol concentration of 14% while Benedryl Decongestant has an alcohol concentration of 5%.

The amount of alcohol you ingest will be one factor in determining your blood alcohol concentration, but another factor is the rate at which your body removes alcohol from your blood, and this differs between individuals. There is no way to determine your blood alcohol concentration short of chemical analysis. Since it is not practical for every driver to do this before they set off, guidelines are produced based on the number of "standard drinks" that an "average person" can consume in an hour before he will be "over the legal limit". It should be noted that some people will need to drink less than the guidelines while there are some people who can consume more.
In Australia, a "standard drink" is one containing 10 g of alcohol.
So, in order for you estimate the number of "standard drinks" you have ingested, you need to know the alcohol concentration in your drink and the volume of the drink you drank. Which is not something you are likely to do while standing at the bar ordering your drink!
For this reason, Government authorities issue the guidelines showing the "standard drink" as volumes of different types of alcoholic beverages:

Alcoholic Beverage	Typical Alcohol Concentration	Standard Drink
light beer	2.7%	1 schooner, 425 mL
ordinary beer	4.9%	1 middy, 285 mL
wine	12%	1 glass, 100 mL
spirits	40%	1 nip, 30 mL
port or sherry	20%	1 glass, 60 mL

In order to maintain a blood alcohol concentration under 0.05%, an "average" person can consume 2 standard drinks in the first hour, followed by 1 drink each following hour. If your legal limit is 0.02%, then even just 1 drink can put you over the legal BAC for driving! And, ofcourse, if your "legal limit" is 0%, you cannot ingest any alcohol at all before driving. Be aware that an average person takes about 1 hour to remove the alcohol in 1 standard drink from their blood stream, so it is quite possible for you to be over the "legal limit" hours after you begin drinking!

Further Reading:
Weight/Volume Percentage Calculations: http://www.ausetute.com.au/wtvol.html
Molarity (mol L^-1 concentration) : http://www.ausetute.com.au/concsols.html

Suggested Study Questions:

1. Determine the mass of alcohol in 100 mL of each of the following drinks:
   • light beer
   • ordinary beer
   • wine
   • spririts
   • port
2. Determine the mass of alcohol in 250 mL of each of the following drinks:
   • light beer
   • ordinary beer
   • wine
   • spririts
   • port
3. Calculate the mass of alcohol present in:
   • 425 mL of light beer
   • 285 mL of ordinary beer
   • 100 mL of wine
   • 30 mL spririts
   • 60 mL port
4. Assuming the recommended dose of Benedryl, or Benedryl Decongestant, is 20 mL, what mass of alcohol is present in each dose?
5. How much of each cough mixture above do you need to consume in order to ingest the same amount of alcohol as present in a standard drink?
6. Explain why the volume of a "standard drink" differs for different types of alcoholic beverage.
7. In one hour, Phyl the Physicist drinks 1 schooner of ordinary beer and 1 glass of wine at Science Expo.
   • What mass of alcohol has Phyl consumed?
   • How many "standard drinks" has Phyl consumed?
8. Also at the Science Expo is Bobby the Biologist who mixes herself a Manhattan; 1 nip of vermouth and 2 nips of whiskey, and a dash of bitters, served in a chilled glass with ice and a cherry garnish.
• What is the minimum mass of alcohol Bobby will consume when she drinks this?
• Approximately how many standard drinks is this equivalent to?
9. Sam the Science student has a cold. She takes a 20 mL dose of Bendryl before going to the Expo. In the same hour, Sam drinks 1 middy of light beer at the Expo.
   • What mass of alcohol has Sam consumed?
   • How many "standard drinks" has Sam consumed?
10. Chris the Chemist is the "designated driver" for his team members at the Science Expo. So Chris drinks a 100 mL cup of mulled wine, which is red wine that has been heated with various spices. Chris thinks the alcohol content of his drink must be less than that of 1 "standard drink". Do you agree? Explain your answer.
11. Assuming "alcohol" refers only to ethanol (ethyl alcohol), convert the following concentrations in w/v% to concentrations of ethanol in mol L^-1 (molarity):
    • light beer 2.7%
    • ordinary beer 4.9%
    • wine 12%
    • spririts 40%
    • port 20%
12. Ethanol is a liquid at room temperature and pressure. Why do you think alcohol concentrations are given in units of grams per 100 mL? Explain your answer

Alkanols vs Alkanals

Question: Differentiate between alkanols and alkanals.

Answer: Alkanols and alkanals are both organic (carbon containing) compounds but they have different functional groups.
Alkanols contain the OH (hydroxyl) functional group.
Alkanals contain the C=O (carbonyl) functional group on a terminal (end) carbon atom of the carbon chain.
Because they have different functional groups they undergo different chemical reactions and will have different physical properties.
The physical and chemical properties of alkanols, for example, can be found at AUS-e-TUTE's page on Properties of Alkanols.

Bioethanol Fireplaces

Ethanol burners are becoming very popular in homes in Australia, often sold as "bioethanol" fireplaces. Although how "bio" your ethanol is really depends on which brand of ethanol or methylated spirits you choose to buy.
Having got some advertising mileage out of sticking the prefix "bio" onto ethanol, the glossy advertising brochure then adds some more enticing words like "eco", "friendly", "green" and/or "smart".
But the real selling point of the slick advertising is that you don't need a flue. No chimney, no pipes, just set your "bioethanol" fireplace up where ever you want it in the room.
Which is really very, very, interesting (for all you Chemists out there).

Chemistry of Combustion
Ethanol combusts (burns) by combining with oxygen gas in the atmosphere.
A balanced chemical equation for the complete combustion of ethanol is:

C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

This tells us that for every 1 mole of ethanol (whether it has the "bio" prefix or not), 2 moles of carbon dioxide gas will be evolved (and yes, that's the same carbon dioxide gas that contributes to the greenhouse effect).

According to the brochure, 5 litres of "bioethanol" would last about 10 hours.
That is, 1 litre of bioethanol keeps your fire going for about 2 hours, just enough to watch a movie.
So how much carbon dioxide will be released into your room while you watch the movie?

First we can use the density of ethanol and the volume of ethanol burnt to calculate the mass of ethanol consumed:

• Density of ethanol is 0.79 g cm³ at 25^oC

• If we let 1cm³ = 1 mL

• then the mass of 1 mL of ethanol is 0.79 g

• so the mass of 1 L of ethanol = 1000 x 0.79 g = 790 g

Now we can calculate the moles of ethanol in the 1 L of "bioethanol" we burnt:

• moles = mass/molar mass

• molar mass = 2 x 12 + 6 x 1 + 16 = 46 g/mol

• so moles of ethanol in 1 L = 790/46 = 17.2 mol

Use the balanced chemical equation to calculate the moles of carbon dioxide produced:

• From the balanced chemical equation, 1 mole of ethanol burns to produce 2 moles of carbon dioxide gas.

• Therefore, 17.2 moles of ethanol burns to produce 2 x 17.2 moles of carbon dioxide gas.

• moles of carbon dioxide produced = 34.4 moles

We can then calculate the volume of carbon dioxide released into your room while you watch the movie:

• At 25^oC, 1 mole of gas occupies a volume of 24.79 L

• So, 34.4 moles of carbon dioxide occupies a volume of 34.3 x 24.79 = 853 L

853 L of carbon dioxide gas sounds like lot!
But is it really? What proportion of the "air" in your room will be carbon dioxide after 2 hours?

Let's calculate the volume of a room:

• A small room is about 3m x 3m x 3m

• or 300cm x 300cm x 300cm = 27,000,000 cm³ = 27,000 L

• So the volume of air in the room before you start burning your ethanol is 27,000 L(ignoring loss of volume due to you and the furniture )

And now we can see what proportion of the "air" in your room will be carbon dioxide after 2 hours:

• Assuming there is no ventilation in the room (all the doors and windows are closed), burning 1 L of ethanol adds about 853 L carbon dioxide gas to the room, so the total volume of gas is now 27,853 L.

• The percentage of that due to the carbon dioxide we have produced is 853/27853 x 100 = 3%

Now that's better, 3% sounds a whole better than 853 L doesn't it?
Or does it?

Did you know that at a concentration of about 1%, carbon dioxide will make you feel sleepy.
At a concentration of about 7%, you can suffocate.
Which makes you think you should probably be opening a window!
Except, wouldn't that defeat the purpose of lighting a fire to keep warm in the first place?

Suggested Study Questions:

1. Draw a structural formula for ethanol.
2. Explain the difference between complete and incomplete combustion of ethanol.
3. How you could you tell by observation whether the ethanol in your "bioethanol" fireplace was undergoing complete combustion or incomplete combustion?
4. The glossy brochure states that your "bioethanol" fireplace will not produce soot. What does this tell you about the type of combustion occurring in the fireplace?
5. If the ethanol in the "bioethanol" fireplace was undergoing incomplete combustion, would the amount of carbon dioxide produced be more or less than that produced during complete combustion?
6. Calculate the moles of carbon dioxide gas that would be produced if you burnt 1 L of "bioethanol" fuel in your fireplace in a room that measured 5m x 7m x 3m
7. What volume of the room in question 6?
8. At 25^oC, how many moles of gas are present in this room from question 6?
9. What percentage of gas in this room from question 6 would be carbon dioxide after you burn 1 L of "bioethanol"?
10. One of your friends suggests that you should take a "bioethanol" fireplace with you on your camping trip because it will be a perfect way to heat your tent. Do you agree with your friend or not? Explain your answer.

Naming Alcohols the IUPAC Way

Alcohols are organic molecules that have the OH (hydroxyl or hydroxy) functional group.
Learn how to apply the IUPAC rules for naming different types of alcohols:

• Naming Straight-Chain Alkanols
• Naming Branched-Chain Alkanols
• Naming Straight-Chain Alkanediols

and learn how to classify alcohols as primary, secondary or tertiary at

• Classification of Alcohols

AUS-e-TUTE Members also have access to additional teaching and learning sources.

Find out about AUS-e-TUTE membership here

and when you're ready to start improving your ability to answer Chemistry questions correctly, you can join AUS-e-TUTE here

AUS-e-TUTE Update

The following resources have been added to AUS-e-TUTE:

• Neutralisation Reactions (tutorial, game, test)
• Acidic, Basic, Neutral Solutions (tutorial, game, test)
• Properties of Alkanes (tutorial, game, test, exam)
• Properties of Alkanols (alcohols) (tutorial, game, test, exam)
• Properties of Alkanoic (carboxylic) acids (tutorial, game, test, exam)
• Properties of Amines (tutorial, game, test, exam)

Syllabus Study Guides have also been updated.