1. Introduction to Organic Pharmacy

2. What are the general characteristics of a Homologous Series? Contain same elements and functional group Series can be represented by a general formula Each homolog differ from one above and one below by a –CH 2 - unit Series of compound can be prepared by similar methods Similar chemical properties Gradual variation in physical properties Lecture : 2

3. Why functional group is important in organic chemistry? Ans. Three reasons Basis for nomenclature To classify Site of reactivity

4. Polarity of Bonds: When two atoms are covalently bonded, the more electronegative atom drags the shared pair of electron towards itself, thus making the bond polar. The higher the polarity, the higher would be the reactivity of the molecule. Hᵟ⁺ - Fᵟ⁻Oᵟ⁻ Hᵟ⁺ Hᵟ⁺

5. Electronegativity: It is a chemical property that describes the tendency of an atom/ a functional group to attract electrons (e-) (or electron density) towards itself. Electronegativity depends on two factors- 1.Atomic number: magnitude/amount of positive charge on the nucleus 2.Atomic radius: distance between the valence electron and nucleus Atoms with higher atomic number and lower atomic radius have higher electronegativity. F˃O ˃Cl,N ˃Br ˃C,H

7. Polar compounds: Molecules which contain polar covalent bonds; they can ionize when dissolved or fused; polar compounds include inorganic acids, bases, and salts. A compound is said to be polar if it satisfies the following two conditions 1.The molecule must contain one/ more polar bonds 2.Center of Positive and negative charge must present in the molecule. O C O ᵟ⁻ ᵟ+ᵟ+ Center of positive charge Two polar carbon- oxygen bonds O H H Center of negative charge Center of positive charge Carbon dioxide Nonpolar as the two negative charges are at the same place as positive charge Water (polar)

9. Van der Waals Force: Short lived intermolecular forces which are believed to be existed between all kinds of atoms, molecules and ions when they are significantly close to each other. Types - A.force between two permanent dipoles B.force between a permanent dipole and a corresponding induced dipole C.force between two instantaneously induced dipoles (London dispersion force).

10. Hydrogen bonding: A hydrogen bond is the attractive force between the lone pair of an electronegative atom and a hydrogen atom that is bonded to another atom.

11. Effects of H-bond on Boiling points : Extra energy needed to break H-bond, so high boiling point. Even though they have same molecular weights. ex.: ethanol =78 0 C, di-methyl ether= -25 0 C (M.W= 46) Effects of H-bond on Solubility: H-bonded substance is usually soluble in another H- bonded substance Ex. : Alcohol – soluble in water Alkane- not soluble in water

12. Factors that influence organic reaction Reaction may or may not occur depending upon the density of electrons at the site of reaction in the substrate. Factors which influence electron density in the substrate are – 1.Inductive effect: The inductive effect refers to the polarity produced in a molecule as a result of higher electronegativity of one atom compared to another.

13. a. + ve inductive effect: atom/group lose electron towards carbon are said to have +ve inductive effect. Eg: alkyl group b. - ve inductive effect: atom/group draws electron away from carbon are said to have - ve inductive effect.eg. F, Cl, I, OH, Br

14. Tertiary alkyl group +I effect > secondary> primary

15. 2. Mesomeric effect: M effect refers to the polarity produced in a molecule as a result of interaction between two π bond or a π bond and lone pair of electrons. a.+ve mesomeric effect: atom/group -lose electron towards carbon are said to have +ve mesomeric effect. Eg: Cl. Br, I, OH,NH 2, b. -ve mesomeric effect: atom/group –draws electron from carbon are said to have -ve mesomeric effect.

16. 3. Electromeric effect The electromeric effect (E effect) refers to the polarity produced in a multiple bonded compound as it is approached by a reagent. When a double/triple bond is exposed to an attack by an electrophile E+, the π electrons which form the π bond are completely transferred to one atom or the other. The electromeric effect is represented as: A B A B + Reagents E+ - :

17. Homolytic and Heterolytic bond fission Homolytic bond fission: in this process, each atom acquires one of the bonding electron Heterolytic Bond fission: here, one of the atom acquires both of the bonding electrons when the bond is broken.

18. CARBANION: Organic ions which contain a negatively charged carbon atom are called carbanions. They are formed by heterolytic bond fission. - C:Z- C:⁻+ Z⁺ Z is less electronegative than carbon CARBONIUM ION: Organic ions which contain a positively charged carbon atom are called carbonium ions or carbocations. They are formed by heterolytic bond fission. -C: Z -C ⁺ + :Z ⁻ Z is more electronegative than carbon Reaction Intermediates Tert- Carbonium ion > secondary > primary ( in terms of stability) ( electron releasing group {+ I) makes it more stable)

19. Classification of Reagents Mainly two types of organic reagents Electrophilic means 'electron-loving'. An Electrophile is a chemical species that is electron-deficient. It will seek out an electron-rich site in an organic molecule. It can be represented by E + Examples : H +, Cl +, Br +, I +, NO 2 +, CH 3 +, CH 3 CO +, C 6 H 5 N 2 + Nucleophile: means "nucleus loving" which describes the tendency of an electron rich species to be attracted to the positive nuclear charge of an electron poor species, the electrophile. It can be represented by Nu: - Examples: Cl -, Br -, I -, OH -,

20. Melting point: The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. Boiling point: The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.

21. Solubility Solubility is the property of a solid, liquid, or gaseous chemical substances called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on temperature and pressure

22. Covalent Bond : results from the overlap of an orbital of one atom with an orbital of another atom Two main types: Sigma bonds (σ): s-s / s-p/ p-p Pi Bonds (π): between two parallel p - orbital Structure of Organic compounds

23. Hybridization is the concept of mixing atomic orbitals to form new hybrid orbital suitable for the qualitative description of atomic bonding properties. Types of hybridization sp3 hybridization sp2 hybridization sp hybridization Hybridization

24. sp3 hybridization Hybridization of one s orbital and three p orbitals. Whenever a carbon is bonded to four another atoms or groups, it uses sp3 hybrid orbitals. Example: hybridization of carbon in methane, ethane, etc.

25. sp2 hybridization Hybridization of one s orbital and two p orbitals. Whenever a carbon is bonded to three other atoms or groups, it uses sp2 hybrid orbitals and one p orbital to form its bonds. Example: hybridization of carbon in ethylene.

26. sp hybridization Hybridization of one s orbital and one p orbital. Whenever a carbon is bonded to two other atoms or groups, it uses sp2 hybrid orbitals and two p orbitals to form the bonds.. Example: hybridization of carbon in acetylene.

27. 4 th lecture

28. Free Radical Free Radical – possess an unpaired electron. Free radical reaction mechanism in Organic Chemsitry :

29. NOMENCLATURE OF ORGANIC COMPOUND

30. You first have to identify the “family” that your molecule belongs to… So, check for functional groups… If there are none, then your molecule is simply an alkane… The name for any organic molecule consists of three basic parts: Prefixes-Parent-Suffix Each part of the name has a purpose. Suffixes on the end of the name of an organic molecule tell you what major family the molecule belongs to The suffix for an alkane is “-ane” The “parent” part of the name tells you how many carbons are in the main chain of the molecule The main chain of the molecule is defined for alkanes as being the longest chain in the molecule

31. The parent is named based on the number of carbons 1 carbon = “meth” So a one-carbon alkane is called methane CH 4 2 carbons = “eth” So a two carbon alkane is called ethane. CH 3 3 carbons = “prop” 4 carbons = “but” 5 carbons = “pent” 6 carbons = “hex” 7 carbons = “hept” 8 carbons = “oct” 9 carbons = “non” 10 carbons = “dec”

32. Name it CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Or, CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3

33. Prefixes are the bits and pieces that are attached to the main chain (parent) of the molecule. An example of a prefix might be a halide attached to the main chain The family called alkyl halides does not have a suffix. Halides are always named as prefixes. Fluorine is called “fluoro” Chlorine is called “chloro” Bromine is called “bromo” Iodine is called “iodo”

34. Putting together a name… The rules for IUPAC nomenclature include: Step 1: Find the main chain Step 2: Number the main chain Step 3: Identify all prefixes and their position numbers Step 4: Write the full name: Prefixes-Parent-Suffix The longest chain in this molecule has seven carbons… and only a halide (which is always named as a prefix). “Bromo hept ane” includes all of the pieces, except for indicating where the bromine is attached... 4-bromoheptane is the complete name

35. Name this – from left to right, the bromine is on position #3 from the other end, the bromine would be on #5 Always aim for the lowest possible number on the first substituent Ans: 3-bromoheptane Name this 1. 2.