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Functional Groups in Organic Compounds:

We have seen that alkanes, alkenes and alkynes are defined by the type of carbon-carbon bonds present in them. 

We can distinguish classes of organic molecules by "functional groups", which largely determine how they react with other compounds and some general properties

functional group - a specific arrangement of atoms in an organic compound that is capable of characteristic chemical reactions.

The carbon-carbon double bond is the functional group defines an alkene

The carbon-carbon triple bond is the functional group that defines an alkyne

If we move away from pure hydrocarbons, there are many more functional groups common to organic chemistry

Note:  -R is commonly used to represent a general alkyl substituent (e.g. methyl, ethyl, propyl, etc...)

1. Alcohols - contains the OH group (frequently used as antiseptics), general structure R-OH

 

CH3OH Methanol - use the suffix ol to name alcohols
(wood alcohol)
CH3CH2OH ethanol
CH3CH2CH2OH 1-propanol - the number indicates the position of the -OH group.  Not necessary with methanol and ethanol because there is only one unique position.
2-propanol (also called isopropyl alcohol and isopropanol - rubbing alcohol)
 

General formula: .  For example with ethanol R = CH3CH2-

2. Ethers:  General structure R-O-R'

Name alkyl groups on both sides in alphabetical order - follow with ether

CH3-O-CH3 dimethyl ether
CH3CH2-O-CH3 ethyl methyl ether
CH3CH2-O-CH2CH3 diethyl ether (anesthetic)

There are many more:  Here is a list of some additional functional groups, you should know the functional group characteristic of each type of organic compound and be able to recognize by the name of an organic compound  (just look at the ending suffix) what group it belongs to.

 

Name of Class General Formula Suffix Example w/ systematic name.  (Common name in parenthesis)
Alkane none -ane ethane,
Alkene -ene ethene (ethylene),
Alkyne -yne ethyne (acetylene),
Arene     benzene
Alcohol -ol ethanol,

Haloalkane (Alkyl halide) "o" in place of "ine" in halogen name. chloroethane (ethyl chloride)

Ether -oxy- (not a suffix really) methoxyethane

more common naming scheme is to call this ethyl methyl ether

Aldehyde -al ethanal,

Ketone -one propanone (acetone),

Amine -amine methylamine,

Carboxylic Acid -oic acid ethanoic acid (acetic acid)

Ester -oate methyl ethanoate

 

Again, remember, functional groups play a major role in determining the physical and especially the chemical properties of organic molecules.  

Demo: Salicylic acid (aspirin) to oil of wintergreen:

---------------->

acid H2SO4, methanol

salicylic acid wintergreen

  

 

Class Some common uses Specific example and use
Alkanes fuels Methane Natural gas burners
Alkenes fuels, manufacture of polymers ethene (ethylene) poly(ethylene)
Alkynes fuels ethyne (acetylene) acetylene torches
Alcohol solvent, antiseptic 2-propanol (isopropanol) rubbing alcohol
Haloalkanes solvent, refrigerant (being phased out) Dichlorodifluoromethane (Freon-12) refrigerant, ozone damage
Aldehyde preservative, perfumes methanal (formaldehylde) preserving biological samples
Ketones perfumes, solvents propanone (acetone) nail polish remover
Amines Fertilizers 1,4 diaminobutane (putrescine)

1,5 diaminopentane (cadaverine)

Putrescine and cadaverine are given off by decaying animal tissue (characteristic smell)
Carboxylic acids Preservatives, soaps, flavorings Ethanoic acid (acetic acid) 5% solution of acetic acid is vinegar
Esters Fragrances See chart below

Some examples of different fragrances mainly esters:

methyl butanoate apple
ethyl butanoate pineapple
propyl ethanoate pear
pentyl ethanoate banana
ethyl formate rum
benzyl ethanoate jasmine

Let's look again at the ingredients list for the mango.  You should be able to recognize molecules from many of the above classes.

a-Terpinolene, Ethyl butanoate, 3-Carene, Ethyl acetate, Ethyl 2-butenoate, a-Terpinene, a-Thujene, Dimethyl sulfide, Limonene, b-Phellandrene, Myrcene, p-Cymen-8-ol, b-Caryophyllene, cis-3-Hexene-1-ol, hexadecyl acetate, 5-Butyldihydro-3H-2-furanone, trans-2-hexenal, Ethyl tetradeconaoate, a-Humulene, Ssabinene, 2-Carene, Camphene, Ethyl octanoate, 4-Isopropenyl-1-methylbenzene 1-Hexanol, g-terpinene, hexanal, Ethyl hexadecanoate, a-Copaene, Hexadecanal, Ethanol, Ethyl propionate, Dihydro-5-hexyl-3H-2-furanone, Carveol, Geranial, Ethyl decanoate, Furfural, Butyl acetate, Methyl butanoate, 2,3, Pentanedione, 1,1, diethoxyethane, pentadecanal, Butyl formate, 1-Butanol, 5-Methylfurfural, Ethyl dodecanoate, 2-Acetylfuran, 2 Methyl-1-butanol, 4-Methylacetophenoen, Acetaldehyde, Cyclohexane

Many organic compounds belong to more than one class:

amino acids - contain a carboxylic acid functionality and an amine functionality.  Amino acids are used by the body to make proteins. Below is a structural formula for glycine, the simplest amino acid. 

Simple sugars such as glucose are polyhydroxyaldehydes.  The hydroxy indicates the OH group of the alcohol.  Below is a structural formula for glucose.