Saturation

What does it mean when a Chemist refers to a molecule as saturated or unsaturated?
How do you test a compound to see if it is saturated or unsaturated?
The answers to these questions, with examples, are given in AUS-e-TUTE's new tutorial Saturated and Unsaturated Organic Compounds

AUS-e-TUTE Members should log-in to access the game, test and exam (with worked solutions) on this topic.

Hydrogenation of Alkenes

How can you convert an unsaturated hydrocarbon such as an alkene, into a saturated hydrocarbon (an alkane)?
With the magic of chemistry (a catalyst), you can add hydrogen across the double bond in an alkene!
AUS-e-TUTE has just added new resources to help our members understand this, and to practice answering test questions. Members should log-in to use these new resources.

If you are not an AUS-e-TUTE member, a "free-to-view" tutorial on this topic is currently available at https://www.ausetute.com.au/hydrogenation.html

Candle-lit Chemistry

What could be more romantic than a candle-lit dinner for two?

Good food, cosy conversation, and the gentle, flickering flames bathing everything in a warm glow.

And all this romance is delivered by the burning of a humble candle, a simple device made up of a block of solid fuel and a wick....

Learn more about the chemistry of candle light in the June 2016 edition of AUS-e-NEWS

You can subscribe to our free newsletter at: http://www.ausetute.com.au/contact.html

Biodiesel

What's the difference between diesel and biodiesel?
I'm glad you asked!
AUS-e-TUTE has just added new resources (tutorial, game, test, exam) to help you learn how to synthesize and characterize biodiesel, as well as to distinguish between diesel and biodiesel.
AUS-e-TUTE Members should log-in to access these new resources: http://www.ausetute.com.au

If you are not an AUS-e-TUTE Member, there is a "free-to-view" biodiesel temporarily available at http://www.ausetute.com.au/biodiesel.html for evaluation purposes.

Want more information about AUS-e-TUTE Membership?
Go to http://www.ausetute.com.au/membership.html

Want to join AUS-e-TUTE?
Go to http://www.ausetute.com.au/register.html

Just want to check out what you can get for free?
Go to http://www.ausetute.com.au

The Smell of Freshness

Organic compounds are added to cleaning products and air fresheners to make the air smell fresh and clean. Scientists are taking a closer look at the chemistry behind the use of these compounds to determine whether they are hazardous to human health.

One of the organic compounds that is widely used to provide the "smell of freshness" is a molecule known as limonene (1-methyl-4-(1-methylethenyl)-cyclohexene). The 2-dimensional structural formula of limonene is shown on the right.

Limonene is a colourless liquid at room temperature and pressure and is found naturally in the rind of citrus fruits such as lemons. It is one of the compounds that contributes to the typical odour of citrus fruit.
Commercial quantities of limonene are produced from citrus fruits using centrifugal separation or steam distillation.

Scientists are studying the reactions of limonene closely because the chemical reactions of this molecule with the ozone in the air in your home are the same as the chemical reactions that occur in the atmosphere that produce secondary organic aerosols (SOAs), microscopic particles suspended in the air, which contribute to the visible haze known as smog in densely populated areas.

The researchers tested various different scenarios for the production of SOAs in the home from limonene and found that the concentration of SOAs produced was between 5μg/cm³ and 100μg/cm³. The acceptable level of aerosols in breathable air is about 12μg/cm³.

The researchers suggest that the best way to reduce SOAs in your home is to either use unscented cleaners or to keep windows open while cleaning. 

Reference:
Somayeh Youssefi, Michael S. Waring. Transient Secondary Organic Aerosol Formation from Limonene Ozonolysis in Indoor Environments: Impacts of Air Exchange Rates and Initial Concentration Ratios. Environmental Science & Technology, 2014; 48 (14): 7899 DOI: 10.1021/es5009906

Further Reading:
Empirical Formula
Molecular Formula
2-Dimensional Structural Formula
Condensed Structural Formula
Skeletal Structural Formula
Percentage Composition
Parts Per Million (ppm) Concentration
Molar Mass

Suggested Study Questions:

1. Write the molecular formula for limonene.
2. Give the empirical formula for limonene.
3. Calculate the percentage of
   • carbon in a molecule of limonene
   • hydrogen in limonene
4. Draw a skeletal structural formula for limonene.
5. Limonene has the IUPAC name 1-methyl-4-(1-methylethenyl)-cyclohexene. Draw the 2-dimensional structural formula for limonene and circle each of the following groups:
   • cyclohexene parent hydrocarbon in red
   • methylethenyl branch in blue
   • methyl branch in black
6. Would you classify limonene as a saturated or unsaturated hydrocarbon? Explain your answer.
7. Convert these concentrations in μg/cm³ to concentrations in parts per million (ppm)
• 5μg/cm³
• 12μg/cm³
• 100μg/cm³
8. Calculate the molar mass of limonene.
9. Calculate the mass of limonene in 100 L of air at 25^oC and 100 kPa for each of the following concentrations:
   • 5μg/cm³
   • 12μg/cm³
   • 100μg/cm³

Propene on Titan

 Titan, one of Saturn's moons, is very special. It is the only satellite in our solar system that has a fully developed atmosphere.
Hydrocarbons were first detected in the atmosphere of Titan by NASA's Voyager 1 spacecraft way back in 1980. Titan's atmosphere is made up of 98.4% nitrogen gas and 1.4% methane. Sunlight breaks this methane apart and the fragments then link up to form chains with 2, 3 or more carbon atoms in the chain. Voyager found the presence of propane and propyne, but not propene.

More recently, NASA's Cassini spacecraft's mass spectrometer data suggested that propene might be present in Titan's upper atmosphere, and in 2013, using a form of infrared spectroscopy, propene was indeed found in Titan's atmosphere.

On planet Earth, propene is second only to ethene as a starting product in the petrochemical industry. About two thirds of all the propene produced is used to make the plastic known as polypropene, or polypropylene, which is used widely in packaging materials.

Reference:
C. A. Nixon, D. E. Jennings, B. Bézard, S. Vinatier, N. A. Teanby, K. Sung, T. M. Ansty, P. G. J. Irwin, N. Gorius, V. Cottini, A. Coustenis, F. M. Flasar. DETECTION OF PROPENE IN TITAN'S STRATOSPHERE. The Astrophysical Journal, 2013; 776 (1): L14 DOI: 10.1088/2041-8205/776/1/L14

Further Reading
http://ausetute.com.au/namctut1.html
http://ausetute.com.au/namsanes.html
http://ausetute.com.au/namsenes.html
http://ausetute.com.au/namsynes.html
http://ausetute.com.au/members/polymers.html
http://ausetute.com.au/members/polythen.html

Suggested Study Questions:

1. What is meant by the term "hydrocarbon"?
2. Give the molecular formula for each of the following hydrocarbons:
   • methane
   • ethane
   • ethene
   • ethyne
   • propane
   • propene
   • propyne
3. Give the structural formula for each of the following hydrocarbons:
   • methane
   • ethane
   • ethene
   • ethyne
   • propane
   • propene
   • propyne 
4. Propene is used to produce polypropene (polypropylene). Draw a representative section of polypropene.
5. Would you describe the polymerisation of propene as an addition polymerisation or as a condensation polymerisation? Explain your answer.
6. Ethene is used to produce polythene or polyethylene. Draw a representative section of polythene.
7. Would you describe the polymerisation of ethene as an addition polymerisation of as a condensation polymerisation? Explain your answer.
8. Both ethene and propene have been found in Titan's atmosphere. Do you think it is likely that polythene and polypropylene will be found in Titan's atmosphere? Explain your answer.