Organic Chemistry Q&A: Boiling Pts, Haloalkanes & Tests

[prime-factor]

Hello. I have a couple of questions.

Why are the boiling points of alkenes lower than alkanes?

My thinking: something with van der waas forces?. Not sure.

Why do haloalkanes have higher boiling points than alkanes?

My thinking: dipole-dipole forces?

What is an experiment that can be used to identify an alkane, an alkene and a carboxyllic acid from each other?

My thinking: Test 1) Bromine water test to identify alkane. Test 2) then to differentiate between carboxyllic acid and alkene, react them with a base, and you will be left with an alkene?

What is a test that can be used to test yeast fermentation?

My thinking: yeast in closed container with sugar. then test alcohol content at certain intervals?. I need some help here on how to design a better test.


Thanks in Advance.

 

[Nino MMP]

The boiling points of alkenes are lower than alkanes because alkenes have weaker intermolecular forces such as Van der Waals forces, whereas alkanes have stronger intermolecular forces such as London dispersion forces. Haloalkanes have higher boiling points than alkanes because the halogen atoms increase the surface area of the molecule and increase the strength of the intermolecular forces. To identify an alkane, an alkene and a carboxylic acid from each other, you can do the following tests: for the alkane, perform a bromine water test; for the alkene, perform a bromine water test followed by an addition of a base (which will cause the bromine to clear); and for the carboxylic acid, perform the bromine water test followed by an addition of an acid (which will cause the bromine to turn back into a dark orange/brown color). To test yeast fermentation, you can measure the rate of carbon dioxide production over time. You can also measure the amount of ethanol produced over time or measure the amount of sugar left in the solution after fermentation has been completed.

 

[Blueshift5]

Hello there,

Thank you for your questions. I am happy to provide some answers and explanations to help clarify your understanding of organic chemistry.

1. The boiling points of alkenes are lower than alkanes because alkenes have a double bond between two carbon atoms, making them more polar than alkanes. This results in stronger intermolecular forces between molecules, leading to a higher boiling point for alkenes.

2. Haloalkanes have higher boiling points than alkanes because the halogen atoms (such as chlorine, bromine, or iodine) in haloalkanes contribute to stronger dipole-dipole interactions and London dispersion forces. These forces increase with the size of the halogen atom, resulting in higher boiling points for haloalkanes compared to alkanes.

3. Your thinking for the experiment to identify an alkane, alkene, and carboxylic acid is correct. The bromine water test can be used to distinguish between an alkane (no reaction), an alkene (decolorization of the bromine water due to addition reaction), and a carboxylic acid (acid-base reaction to form a salt and water).

4. A test that can be used to test yeast fermentation is the production of carbon dioxide gas. As you mentioned, yeast can be placed in a closed container with sugar, and the production of carbon dioxide can be measured using a gas collection tube or pressure sensor. Other tests that can be used include measuring the change in pH or the production of ethanol.

I hope this helps answer your questions. If you have any further questions, please don't hesitate to ask. Happy experimenting!