Thursday, June 2, 2011

Organic Chemistry: Functional Groups

Functional groups- specific group of atoms in a molecule & gives the molecule the ability to react in a specific manner/give it special properties.
They're organic compounds that contain elements other than Carbon and Hydrogen. It can include single atoms (Ex. Cl, Br) or groups of atoms (Ex. NO2, NH2)
Examples include alcohol, aldehydes, amines, ethers, ester, etc.


The main ones we will focus on are:
1) Halides & Nitro Compounds
2) Alcohols
3) Aldehydes & Ketones


Halides & Nitro Compounds:
It's named similar to hydrocarbons and are attached to alkenes, alkanes, and alkynes.
How to name them? Main chain names receieve the following prefixes if that certain group is attached:
Halogens:
F=fluoro
Cl= chloro
Br= bromo
I= iodo
Nitro:
NO2= nitro


Use a number to indicate where it's attached to the hydrocarbon chain. If more than one is present, use prefixes di, tri, tetra, etc. If it contains more than one group, put them in alphabetical order. Number from the end which gives the lowest set of numbers.


Properties of Halogenated Compounds:
1) Tend to be insoluble in water (similar to alkanes)
2) Fluorinated compounds tend to be unreactive (inert)
Ex. Teflon is resistant to reactions with most chemicals
3) Chloro and bromo compounds are susceptible to chemical attacks under drastic conditions
4) Iodo compounds are more reactive and can be easily replaced by other functional groups


Properties of Nitro Compounds:
1) Soluble in water
2) Unreactive to chemical attacks except under drastic conditions
3) Explosive (Ex. TNT (trinitrotulene) and nitroglycerine)
4) Pleasant odour.


Alcohols- organic compounds containing OH group
How to name it? Number the hydrocarbon chain and give the lowest possible number for the OH group. Put the number before the name of the parent hydrocarbon, separated by a dash. Alkyl groups are placed in front of number for the OH. Change the 'e' ending to 'ol'. An example of an alcohol is in the picture on the left which is ethanol. And oh-so happens to look like a dog. LOL.


Properties of Alcohols:
1) OH group tends to make alcohols soluble in water. Non polar hydrocarbons chains make it insoluble.
Methanol, ethanol, and propanol are highly soluble in water due to hydrocarbon being small. Butanol is moderately soluble. Penntanol and high are insoluble in water.
2) Poisonous to some degree. Includes ethanol (in alcoholic beverages)


Multiple-OH:
If a compound has more than one group, number both and add diol, triol, etc endings. 


Aldehydes- organic compound containing a C=O group at the end of the hydrocarbon chain
It follows the standard rules but changes the parent chain ending to 'al'. The simplest of this group is methanal (formaldehyde).


Ketones-organic compound containing C=O group at a position other than the end of the hydrocarbon chain.
It follows the standard rules but add 'one' at the ending to the parent chain.







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