Sancho's Organic Notes Olevel - Form Four,
Organic chemistry is the study of the structure, properties, composition, reactions, and synthesis of compounds that contain carbon atoms, usually bonded to hydrogen, oxygen, nitrogen, sulfur, and other elements.
The compounds obtained from minerals, that is, non living sources are known as in organic compounds. The compounds derived from animal and vegetable sources have almost similar composition of elements. Nearly, all of them were composed of carbon, hydrogen, and oxygen elements. In view of the similarity of composition, the compounds obtained from living organism that is, animals, and plants, were collectively called organic compounds.
Organic chemistry: Is the study of hydrocarbons (compounds of carbon and hydrogen elements) and other compounds regarded as derivatives of hydrocarbons.
It may be noted that some organic compounds may also contain elements like nitrogen, oxygen, sulphur, halogens, e.t.c. besides carbons and hydrogen.
Organic chemistry: Is defined as the study of carbon and its complex compounds, however there are several exceptions: Carbon monoxide, CO; Carbonates, CO3; Carbon dioxide, CO2; Bicarbonates, NaHCO3, Carbide, CaC2; Cyanides, KCN; Carbon disulphide, CS2; Thiocyanates, NaSCN.Complex compounds of carbon are the compounds in which carbon is tetravalent and can form chain or ring.
Organic chemistry: can also be defined as a branch of chemistry that involves the study of preparation, structure, properties, composition, and reactions of organic compounds.
The carbon atom has unique or peculiar properties because of the following:
(a) It can use wide range of oxidation states
(b) Its ability to undergo catenation, the atoms of this element is able to attach themselves to one another and also to some other atoms. This may lead to the formation of very long chains of carbon atoms. The atoms can also form rings of all sizes.
(c) It is center of the first short period of (first element of group IV) periodic table.
Importance of organic compounds
(a) Medicines; antibiotics like penicillin
(b) Food; proteins, fat oil, carbohydrates
(c) Dyes and perfumes
(d) Disinfectant and pesticides example DDT, naphthalene
(e) Daily use; soap, rubber, paper
(f) Explosives; picric acid
(g) Textiles; cotton, silk, nylon.
Sources of organic compounds
i. Petroleum, coal (contains about 85% - 95% of carbon), and naturals gas.
ii. Plants and animals; synthesize many useful carbon compounds such as sugars, starches, drugs.
iii. Synthetic compounds e.g. nylon, polyesters, dyes, colours, rubber, alcohols, etc.
HYDROCARBON
Are the compounds containing hydrogen and carbon only.
That is, hydrocarbon has the molecular formula CxHy, x and y being whole numbers.
There are two types of hydrocarbons:
(a) Aliphatic hydrocarbon
(b) Aromatic hydrocarbon
(a) Aliphatic hydrocarbons: Are compounds containing straight or branched of carbon atom skeletons with appropriate number of H – atoms and functional groups. Or, are all organic compounds whose molecules are composed of chains of carbon atoms.
There are three main families of hydrocarbons. These are;
i. Alkane (Paraffin) – CnH2n+2
ii. Alkene (Olefins) – CnH2n
iii. Alkyne (acetylene) – CnH2n – 2
(b) Aromatic (Arenes) hydrocarbons: Are those compounds whose molecules contain six – member rings of atoms. Example, benzene On a broad basis, hydrocarbons may be classified into two groups:
(i) Saturated hydrocarbons: Are the hydrocarbons, which contain maximum possible numbers of hydrogen atom. Or, are hydrocarbons formed if all the four possible bonds of every carbon atom are joined using single bond to another carbon atom or hydrogen atom.
(ii) Unsaturated hydrocarbons: Are hydrocarbons in which some atom(s) are not eerting all of its combining power with other atoms. They have a double (C =C) or triple (C= ) bond between any of the carbon atom.
HOMOLOGOUS SERIES
Are series of compound related to each other and differ by CH2.
Properties of homologous series
i. All members confirm same general molecular formula e.g. Alkane, CnH2n+2.
ii. All members differ to the next member by CH2.
iii. All members have the same chemical properties but differ in their vigorous.
iv. The physical properties of the members change gradually along the series i.e. they vary
v. The method of preparation for all members is the same.
vi. They have the same functional group.
