Chemistry • Chemistry is the study of the substances, specially their structure, properties, transformations and the energy changes accompanying these transformation.
Organic Chemistry • The study of Carbon Compounds or better to say the chemistry of hydrocarbons and their derivatives.
ATOMIC STRUCTURE • Atom: Smallest indivisible particle of an element • Molecule: Smallest particle of matter
Types of Bonding • Ionic bonding • electron is fully transferred from metal to non-metal • binding is by electrostatic attraction.
Ionic Bonding Sodium Atom Fluorine Atom
Ionic Bonding (2) Sodium ion Fluoride ion Attraction between the two ions is electrostatic -- Ionic Bond
. . H H A SIMPLE COVALENT BOND A pair of electrons is shared between the two bonded atoms.
A SIMPLE COVALENT BOND Bonded pair H H
A LEWIS DIAGRAM .. (note use of lines for bonds) H O H .. COVALENT BONDS CONSTRUCTED FROM LEWIS DOT SYMBOLS .. . . . . H O H ..
DRAWING CONVENTIONS 1. A shared pair (bond) is drawn as a line. C O 2. An unshared pair is shown as a pair of dots. N : 3. The diagram includes formal charges(later). .. + H O H H
Bonding patterns • Carbon 4 bonds • Nitrogen (phosphorus) 3 bonds • Oxygen (sulfur) 2 bonds • Halogen (F, Cl, Br, I) 1 bond • Hydrogen 1 bond
Types of Carbons Primary (1°) – attached to only one other carbon Secondary (2°) – attached to two other carbons Tertiary (3°) – attached to three other carbons Quaternary (4°) – attached to four other carbons
Hydrocarbons Aliphatic alkanes – contain only single bonds (saturated) alkenes – contain at least one double bond (unsaturated) alkynes – contain at least one triple bond Aromatic contain a benzene ring
Hydrocarbons • Alkanes contain only single ( ) bonds and have the generic molecular formula: [CnH2n+2] • Alkenes also contain double ( + )bonds and have the generic molecular formula: [CnH2n] • Alkynes contain triple ( + 2)bonds and have the generic molecular formula: [CnH2n-2] • Aromatics are planar, ring structures with alternating single and double bonds: eg. C6H6
Types of Hydrocarbons Each C atom is tetrahedral with sp3 hybridized orbital. They only have single bonds. Each C atom is trigonal planar with sp2 hybridized orbitals. There is no rotation about the C=C bond in alkenes.
Types of Hydrocarbons Each C atom is linear with sp hybridized orbitals. Each C--C bond is the same length; shorter than a C-C bond: longer than a C=C bond. The concept of resonance is used to explain this phenomena.
Alkanes 1 meth methane CH4 2 eth ethane C2H6 3 prop propane C3H8 4 but butane C4H10 5 pent pentane C5H12 6 hex hexane C6H14 7 hept heptane C7H16 8 oct octane C8H18 9 non nonane C9H20 10 dec decane C10H22
Naming Alkanes C1 - C10 : the number of C atoms present in the chain. Each member C3 - C10differs by one CH2 unit. This is called a homologous series. Methane to butane are gases at normal pressures. Pentane to decane are liquids at normal pressures.
Constitutional Isomers • Substances which have the same molecularformula but a different structural formula. • Isomers differ in connectivity.
Isomerism • Molecules which have the same molecular formula, but differ in the arrangement of their atoms, are called isomers. • Constitutional (or structural) isomers differ in their bonding sequence. • Stereoisomers differ only in the arrangement of the atoms in space. =>
Many things in nature look similar, but they are completely different !
Isomers Constitutional structural connectivity ≠ Stereoisomers connectivity = orientation≠ Enantiomers Non-superimposable mirror image Diastereomers not mirror images
A compound can have more than one name, but a name must unambiguously specify only one compound A C7H16 compound can be any one of the following: email@example.com
Diastereomers Cis-trans isomers are also called geometric isomers. There must be two different groups on the sp2 carbon.
Functional Groups • An atom or group of atoms which makes an organic compound reactive and decides its functions (properties) is called a Functional group. • In an organic compound, the alkyl group determines the physical properties whereas the functional group determines the chemical properties of the compound. • A Functional group can be introduced by displacing hydrogen of the hydrocarbon. • The functional groups are directly attached to the carbon of the organic compound.
The basic structure of testosterone (male hormone) and estradiol (female hormone) is identical. • Both are steroids with four fused carbon rings, but they differ in the functional groups attached to the rings. • These then interact with different targets in the body.
6 functional groups, all hydrophilic • hydroxyl group (-OH), a hydrogen atom forms a polar covalent bond with an oxygen which forms a polar covalent bond to the carbon skeleton. • Because of these polar covalent bonds hydroxyl groups improve the water solubility of organic molecules. • Organic compounds with hydroxyl groups are alcohols and their names typically end in -ol.
A carbonyl group (-CO) consists of an oxygen atom joined to the carbon skeleton by a double bond. • If the carbonyl group is on the end of the skeleton, the compound is an aldelhyde. • If not, then the compound is a ketone. • Isomers with aldehydes versus ketones have different properties.
A carboxyl group (-COOH) consists of a carbon atom with a double bond with an oxygen atom and a single bond to a hydroxyl group. • Compounds with carboxyl groups are carboxylic acids. • A carboxyl group acts as an acid because the combined electro-negativities of the two adjacent oxygen atoms increase the dissociation of hydrogen as an ion (H+).
An amino group (-NH2) consists of a nitrogen atom attached to two hydrogen atoms and the carbon skeleton. • Organic compounds with amino groups are amines. • The amino group acts as a base because amino groups can pick up a hydrogen ion (H+) from the solution. • Amino acids, the building blocks of proteins, have amino and carboxyl groups.
A sulfhydryl group (-SH) consists of a sulfur atom bonded to a hydrogen atom and to the backbone. • This group resembles a hydroxyl group in shape. • Organic molecules with sulfhydryl groups are thiols. • Sulfhydryl groups help stabilize the structure of proteins.
A phosphate group (-OPO32-) consists of phosphorus bound to four oxygen atoms (three with single bonds and one with a double bond). • A phosphate group connects to the carbon backbone via one of its oxygen atoms. • Phosphate groups are anions with two negative charges as two hydrogens have dissociated from the oxygen atoms. • One function of phosphate groups is to transfer energy between organic molecules.
Functional Groups firstname.lastname@example.org
Functional Groups email@example.com
ALCOHOL FUNCTIONAL GROUP R –O H
Classification • Monohydric Alcohols • Polyhydric Alcohols - Dihydric Alcohols (Ethylene Glycol) - Trihydric Alcohols (Glycerol)