CARBON AND ITS COMPOUNDS PRASHANTH C P

CARBON IS UNIQUE Carbon is unparalleled in its ability to form large, complex, and diverse molecules Although cells are 70–95% water, the rest consists mostly of carbon-based compounds Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds

Organic chemistry is the study of carbon compounds Most organic compounds contain hydrogen atoms in addition to carbon atoms Vitalism, the idea that organic compounds arise only in organisms, was disproved when chemists synthesized the compounds

Organic chemistry is the branch of chemistry that specializes in carbon compounds, also known as organic molecules. Plastic, rubber, and gasoline are important carbon compounds. Scientists classify the organic molecules in living things into four basic groups: carbohydrates, proteins, fats, and nucleic acids.

Carbon atoms can form diverse molecules by bonding to four other atoms Electron configuration is the key to an atom’s characteristics Electron configuration determines the kinds and number of bonds an atom will form with other atoms

The Formation of Bonds with Carbon With four valence electrons, carbon can form four covalent bonds with a variety of atoms This tetravalence makes large, complex molecules possible

In molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shape However, when two carbon atoms are joined by a double bond, the molecule has a flat shape

Carbon chains form the skeletons of most organic molecules Carbon chains vary in length and shape

some common molecules that contain carbon

Carbon molecules come in three basic forms: straight chains, branching chains, and rings. All three forms are found in important biological molecules.

SAPONIFICATION

Cleansing action of soap

SYNTHETIC DETERGENT

Carbon’s Bonding Pattern Carbon has 4 electrons in its outer shell. To satisfy the octet rule, it needs to share 4 other electrons. This means that each carbon atom forms 4 bonds. The 4 bonds are in the form of a tetrahedron, a triangular pyramid. Carbon can form long chains and rings, especially with hydrogens attached. Compounds with just carbon and hydrogen are “hydrocarbons”: non-polar compounds like oils and waxes.

Functional Groups Most of the useful behavior of organic compounds comes from functional groups attached to the carbons. A functional group is a special cluster of atoms that performs a useful function.

Structural Isomers 1.Pentane and 2-methylbutane are both C 5 H

Alkanes Alkenes Alkynes Aromatics C

R  X R means alkyl group X is F, Cl, Br or I CH 3 CH 2 Cl Chloroethane CCl 4 Tetrachloromethane (Carbon tetrachloride using CHM 111 system) Haloalkanes

Alcohols R  OH R means alkyl group CH 3 CH 2 OH Ethanol (or Ethyl Alcohol)

Carbonyl Group - C - || O

Carboxylic Acids R  C  OH || O Ethanoic acid (or Acetic acid) CH 3 – C – OH || O

Esters R  C  O  R´ || O Methyl ethanoate (methyl acetate) CH 3 – C – O – CH 3 || O

How to Make an Ester Combine an acid and and an alcohol with the elimination of water to form ester linkage CH 3 – C – O – H H – O – CH 3 - H 2 O O ||

– Three Dimensional Shape of Molecules Virtually all molecules possess a 3-dimensional shape which is often not accurately represented by drawings It was proposed in 1874 by van’t Hoff and le Bel that the four bonds around carbon where not all in a plane but rather in a tetrahedral arrangement i.e. the four C-H bonds point towards the corners of a regular tetrahedron

– Ionic Bonds When ionic bonds are formed atoms gain or lose electrons to achieve the electronic configuration of the nearest noble gas – In the process the atoms become ionic The resulting oppositely charged ions attract and form ionic bonds This generally happens between atoms of widely different electronegativities Example – Lithium loses an electron (to have the configuration of helium) and becomes positively charged – Fluoride gains an electron (to have the configuration of neon) and becomes negatively charged

– Covalent Bonds Covalent bonds occur between atoms of similar electronegativity (close to each other in the periodic table) Atoms achieve octets by sharing of valence electrons Molecules result from this covalent bonding The usual way to indicate the two electrons in a bond is to use a line (one line = two electrons)

The Formation of Bonds with Carbon With four valence electrons, carbon can form four covalent bonds with a variety of atoms This tetravalence makes large, complex molecules possible