[Chemistry Class Notes] on Classification of Chemical Compounds Pdf for Exam

A chemical compound is a chemical substance that has molecules with two or more elements. Matter consists of atoms of various elements. Elements either exist as pure forms or in a combined form. The combined form is known as a chemical compound. A pure element is made up of atoms that are found in that element. Each element gets its characteristic properties due to the characteristic nature of the atoms that comprise that element. For instance, atoms of iron are very different from atoms of gold. Each atom has its symbol which is often an abbreviation of its name or its name in Latin. 

Chemistry involves studying how atoms of various elements combine to form compounds. Ethanol for instance is formed from the elements carbon, hydrogen, and oxygen. It contains specific ethanol molecules. The chemical formula of ethanol C₂H₅OH indicates the types and the numbers of atoms that are present in the compound. Water which has a chemical formula H₂O consists of 2 atoms of hydrogen and one atom of oxygen. Salt or sodium chloride is a compound that has sodium and chlorine in an equal ratio. It has sodium ions that are positively charged and chlorine ions that are negatively charged. 

From these examples, we can get a basic classification of compounds- covalent or molecular compounds and ionic compounds, compounds that comprise molecules are called molecular compounds, and compounds that comprise ions are called ionic compounds. 

Classification of Pure Substance

Matter can be categorized into various categories. In chemistry, the category that we begin from is that of pure substance and mixtures. A pure substance is a chemical material that has a consistent composition throughout. All parts of a pure substance will have the same chemical properties regardless of where it is obtained. Pure substances are further classified as elements and compounds. Elements are chemicals that cannot be broken down into smaller units. While substances that can be broken down into their constituent units are called compounds.  

Classification of Metal Carbonyls

Metal carbonyls are a class of organometallic compounds. They are of two types: mononuclear carbonyls that have one metal atom per molecule and polynuclear carbonyls that have two or more metal atoms per molecule. 

Classification of Alkyl Halides

Alkyl halides or haloalkanes are compounds in which hydrogen atoms in an alkane are replaced by atoms from the halogen family such as chlorine, fluorine, etc. Haloalkanes are of 3 types primary, secondary and tertiary. In primary haloalkanes, the carbon connected to the halogen on one end is attached to a single alkyl group on the other end. In secondary, the carbon connected to the halogen is connected to two same or different alkyl groups. In tertiary alkyl halides, the carbon atom is connected to three same or different alkyl groups. 

Classification of Carboxylic Acid

Carboxylic acids are those organic compounds in which the carbon atom is connected to the oxygen atom by a double bond and a hydroxyl group by a single bond. Carboxylic acids are categorized as aromatic, unsaturated, and saturated aliphatic, amino acids, keto and hydroxy acids, and polycarboxylic acid. 

Classification of Organic Compounds

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1. Open Chain Compounds: Also called acyclic or aliphatic organic compounds, they consist of chains that may be straight or branched. 

2. Closed Chain Compounds: Also called alicyclic or ring organic compounds, they consist of atoms of carbon that are joined to each other in a ring structure. If the chain also contains atoms that are not carbon then the ring is heterocyclic. 

3. Aromatic Compounds: Aromatic compounds are organic compounds with a unique set of properties. They also gave a ring structure. They can also have more than one atom in the ring. 

Classification based on the functional group: An atom or a set of atoms that are combined in a particular way to an organic compound is called a functional group. These groups impart specific chemical properties to the compounds they are joined to. Some examples of functional groups are: -OH,-COOH et al.

4. Homologous Series: A series of organic compounds where each part has the same functional group that imparts its special characteristics. For instance: alkanes, haloalkanes, amines, etc.  

Fun Fact

An organic compound was first synthesized from inorganic substances by the German chemist Friedrich Wöhler in 1828. This discovery was accidental. He synthesized urea by mixing the salts silver cyanate and ammonium chloride. From this result, he proposed that atoms used different methods of arranging themselves into molecules and that the characteristics of these molecules are based on the molecular structure. Other chemists followed suit and by the 1860s, the notion that some magical “vital force” was required for the formation of organic compounds was debunked.