It is the study of carbon- containing molecules known as organic compounds.

Carbon Compounds 19th century – it was thought that organic compounds come from living things and those that come from

nonliving things were called inorganic compounds. 1828 – A German chemist Friedrich Wohler disproved this idea by synthesizing urea, an organic

compound from an inorganic substance, ammonium cyanate. All organic compounds contain element carbon are referred to as carbon compounds.

Why Carbon????o It has a special property to form bonds in many different ways while satisfying its bonding power of four

for each atom.o Compounds of carbon maybe in the form of chains, long continuous chains or branched chains.o Some chains may form to produce ring compounds.o Carbons form strong covalent bonds to each other while also holding the atoms of other nonmetals

strongly.Characteristics of Organic Compounds

Insoluble in water Low melting and boiling points Combustible

Does not conduct electric current Easily decompose when heated Covalent bonding

Isomerism Isomerism is another reason why there are so many organic compounds. Isomers

are compounds with identical molecular composition but their structures are arranged differently. Depending on how they are arranged, they may have similar or different properties.

Examples of isomers:

Butane and 2-methyl propane both Ethanol and dimethyl ether both have the molecular formula C4H10 have the molecular formula C2H6O.

HydrocarbonsHydrocarbons are the simplest organic compounds . Containing only carbon and hydrogen, they can be

straight-chain, branched chain, or cyclic molecules.FormulaStructural Formula

H H H H | | | |H-C-C-C-C-H | | | | H H H H

butane

H | H H-C-H H | | |H-C---C---C-H | | | H H H

2-methyl propane

H H | |H-C-C-O-H | | H H

ethanol

H H | |H-C-O-C-H | | H H

dimethyl ether

Condensed Structural Formula

The Uniqueness of CarbonThe great number of carbon compounds is possible because of the ability of carbon to form strong covalent bonds to earth other while also holding the atoms of other nonmetals strongly. Chains of carbon atoms can be thousands of atoms long, as in polyethylene. Polyethylene chain: H H H H H H H H H H H | | | | | | | | | | |H-C-C-C-C-C-C-C-C-C-C-C-etc. | | | | | | | | | | | H H H H H H H H H H H

IsomersIsomerism is another reason why there are so many organic compounds. Isomers are compounds with identical molecular composition but their structures are arranged differently. Depending on how they are arranged, they may have similar or different properties. Because the number of carbons per molecule increases as the compound gets more complex, the number of possible isomers for any given formula becomes very, very large.

Formula Number of Isomers

C8H18 18

C10H22 75

C20H42 366,319

C40H82 6.25 x 1013 (approx.)

Such a huge number of organic compounds requires organization. They are sorted into organic families defined by functional groups. Functional groups are small structural units within molecules at which most of the compound's chemical reactions occur. For example, two of the most important families are the alcohols and the carboxylic acids. Their functional groups, the alcohol group and the carboxyl group, respectively, distinguishes them from the rest of the other types of organic compounds.

alcohol group methanol (methyl alcohol)

carboxyl group acetic acid (ethanoic acid)

Important Families of Organic CompoundsSymbolism shown below that you may not understand will be explained later in this topic

Hydrocarbons Only C and H present

Alkanes Only single bonds

Alkenes Double bond(s) between two carbons

Alkynes Triple bond(s) between two carbons

Aromatic

Alcohols

Ethers

Aldehydes

Ketones

Carboxylic Acids

Esters

Amines

Amides

R, R', and R'' represent hydrocarbon groups (alkyl groups)The type of properties associated with a compound is different depending on the family it is in. For example, the alkanes have just C-C and C-H single bonds. Since C and H are so alike in electronegativity, they are least able to attract ions or polar molecules, and least able to interact with them. The significance of this will be explained later.

Condensed StructuresTo save space and time, condensed structures may be used to simplify the drawing and writing of structural formulas of organic compounds. C-H bonds are understood, and CH3 means that three hydrogen atoms are bonded to a carbon atom. For example:

CH3 is understood to be

H |H-C- | H

CH3CH2OH is understood to be

H H | |H-C-C-O-H | | H H

CH3OCH2 is understood to be H H

| |H-C-O-C-H | | H H

Functional Groups and Polar ReactantsWhen a polar group of atoms, like the OH group or NH group are attached to a carbon, the molecule has a polar site. It may undergo chemical reactions when it attracts polar and ionic reactants, but it will usually be near this functional group. This is why compounds with the same functional group have similar chemical properties, or kinds of reactions. For example, in the amine group, both methylamine and ethylamine give the same kinds of reactions. CH3NH2 + HCl ==> CH3NH3

+ + Cl-

methylamine + hydrogen chloride ==> methylammonium ion + chloride ion

CH3CH2NH2 + HCl ==> CH3CH2NH3+ + Cl-

ethylamine + hydrogen chloride ==> ethylammonium ion + chloride ion

Only the NH2 group of the amines change in the previous two reactions, and it changes the same way in both.

The Symbol R in Structural FormulasThe symbol R, stands for the word radical, and in organic chemistry, represents alkane-like groups. It is sometimes used to simplify equations or to summarize them. For example, to summarize the two equations in the previous sections, you may write: RNH2 + HCl ==> RHN3 + Cl-

The R takes care of any alkane group that you may substitute in. It takes care of all the equations, including methylamine, ethylamine, propylamine, butylamine, etc. It gives a simpler view of how one group, not just the individual compound, changes into another and how each group affects its properties.