By Gurpreet & Aditya

Answering “what”

Alcohol: An organic compound characterized by the presence of a hydroxyl functional group, R-OH

Hydroxyl group: an OH-functional group characteristic of alcohols.

Impacts on Society and Health Society:

Every year roughly 5000 people under age of 21 die because of alcohol related car accidents in USA.

Every 90 seconds, someone is injured from a drunk driving accident.

Health:

Drinking alcohol leads to high blood pressure, stroke, cancer (mouth, liver), and weak immune system.

It is also the main reason for change in mood/behaviour.

Naming Alcohols (one hydroxyl group) Use same naming scheme as hydrocarbons. For

example, methane for hydrocarbon with 1 carbon and 4 hydrogens. However, when you have one –OH group instead of one hydrogen, you replace the “e” from methane with “ol” For example, CH3OH would be methanol.

If you have for than one carbon atoms, make sure to identify where your –OH group is attached using numercal numbers. For example, 2-propanol.

Practice

Methanol 2-propanol

Polyalcohol Poly means more than one, therefore polyalcohol

means an alcohol that contains more than one hydroxyl functional group.

Naming Polyalcohol

Use the same naming scheme as hydrocarbons but add “di”, “tri” etc. at the end followed by “ol”. For example, if 2 hydrogens from two carbons of ethane are replaced by –OH groups, the name would be “1,2-ethanediol,” where “di” represents the number of –OH groups present.

Make sure to use numerical number to identify where the –OH group is attached in the parent chain.

Practice

1,2-ethanediol

Structure and Formula The structure is same as hydrocarbons but you need to

attach right –OH group at right place. For example, methanol’s structural formula will have one Carbon attached to 3 hydrogens and one –OH group. The chemical formula can be written by counting number of C’s, H’s and O’s. It would be CH4O or CH3OH.

Lets do an example.

Cyclic alcohols and naming Cyclic alcohol: an alcohol that contains a cyclic ring.

To name them, you put “cyclo” after numerical number if have any with the given name.

If there is any other branch such as “methyl,” put it before everything else with numerical value to identify its location.

OH

1,2-cyclohexanediol

OH

OH

OH

CH34-methyl-1,2-cyclohexanediol

Aromatic Alcohol/Naming an alcohol that contains a benzene ring.

To name it, use prefix “hydroxy” with suffix “benzene”

Hydroxybenzene is also called phenol and it has one –OH group attached to it.

If you have more than one –OH groups, use “di”, “tri” etc before of “hydroxy” to indicate quantity of them and use numerical value to show where they are located. For example, 1,2-dihydroxybenzene

Practice

Phenol or Hydroxylbenzene

1,2-dihydroxylbenzene

Physical Properties of Alcohols By taking away one hydrogen and replacing it with

-OH, the main change which happens is the type of molecule. It becomes polar from non polar. For example, methane is non polar however, methanol is polar.

In addition, hydrogen bonding occurs in hydroxyl groups of molecules.

Hydrogen Bonds in Methanol

Boiling/Melting Point Alcohols have high melting and boiling points as

compare to hydrocarbons because of the presence of strong hydrogen bonding in it.

You need more energy to break that hydrogen bonding and this explains high boiling/melting point.

Name Formula Boiling Point (C)

Methanol CH3OH 65

Ethanol C2H2OH 78

Name Formula Boiling Point (C)

Methane CH4 -89

Ethane C2H6 -164

Solubility (like dissolves like) Alcohols are unique in a way that they can dissolve

both non-polar and polar substances.

This can be explained in terms of presence of –OH which is polar and dissolves polar and same with hydrocarbon but for non polar.

However, solubility of alcohols is determined by the stronger of the two forces. (Dispersion for hydrocarbon and hydrogen bonding for –OH)

Therefore, longer the chain, less soluble it is in water.

Solubility animation http://ibchem.com/IB/ibnotes/full/bon_htm/solubilit

y.htm