Organic Chemistry Lecture Notes PDF

‫بسم هللا الرحمن الرحيم‬  Steric Effect ◼ Steric effect is an effect on relative reaction rate caused by the space-filling properties of those parts of a molecule attached at or near the reacting site. ◼ Steric effect depends on the size of the groups or atoms and t...

‫بسم هللا الرحمن الرحيم‬  Steric Effect ◼ Steric effect is an effect on relative reaction rate caused by the space-filling properties of those parts of a molecule attached at or near the reacting site. ◼ Steric effect depends on the size of the groups or atoms and the amount of space they occupy. ◼ And is Completely independent of electronic effects. 2  Steric Hindrance ◼ Steric Hindrance means that the spatial arrangement of the atom or groups at or near the reacting site of a molecule hinders or retards a reaction. ◼ Steric hindrance in a molecule usually becomes sever as a result of presence of very bulky groups in the molecule. ◼ Steric hindrance in a molecule usually results in slowing down the rate of the reaction. ◼ Actually the reaction may be affected, resulting in the formation of products entirely different from the ones expected. 3  CH2=CH CH = CH2 CH3 CH3 C1 CH3 CH2 C C CH2 CH3 C CH3 CH3 4 Classification of Organic Compounds Functional Principal groups Series Functional groups 6  Functional groups ◼ They are the reactive part of a molecule which identifies it as belonging to a particular organic family. General formula Functional group Class Alkanes R-H Ane Alkenes R-CH=CH2 (C=C) Double bonds Alkynes Triple bonds R C C H CC Arenes Ar-H Aromatic ring (s) Alkyl or aryl halides R-X or Ar-X X=Fluro, chloro, bromo, iodo groups Alcohols or phenols R-OH or Ar-OH (OH) Hydroxyl group Ethers (aromatic or R-O-R' or Ar-O-R or (-O-) Ethers group aliphatic) Ar-O-Ar Amines R-NH2 or Ar-NH2 (-NH2) Amino group Aldehydes R-CHO or Ar-CHO (-CHO) Aldehydic Ketones R-CO-R or Ar-CO-R or Ar-CO-Ar (-CO-) Ketonic group Carboxylic acids R-COOH or Ar-COOH (-COOH) Carboxylic Amides R-CO-NH2 or Ar-CO-NH2 (-CONH2) Amide group Esters R-COO-R' or Ar-COO-R or Ar-COO-Ar (-COO-) Ester group 7 Nitro compounds R-NO2 or Ar-NO2 (NO2) Nitro group  Class Functional Group Suffx used O carboxyli acid sulphonic acid C OH - oic acid SO3H - sulphonic acid O ester C O alky oate O Acid halide C X oyl halide O amide C NH 3 amide nitrile CN nitrile O aldehyde C H al O ketone C one alcohol OH ol amine N amine ethers O (ehter) alkene C C ene alkene C C yne Principal Series 9  Principal Series Acyclic (open chain) Cyclic Acyclic Saturated unsaturated may contain one or more All bonds are − bonds Double or triple bonds10  Cyclic Carbocyclic Heterocyclic Carbocyclic Aromatic Alicyclic 11  Heterocyclic Saturated unsaturated All bonds are − Partial or complete unst. bonds ◼ N.B. The division of organic compounds into aliphatic and aromatic series is particularly useful. ◼ Hence the separate study of aliphatic and aromatic compounds has been preferred in our courses. 12  In this Lecture 13 ISOMERS  They are the compounds that have identical chemical and molecular formulas but differ in the nature of sequence of bonding of their atoms or in their arrangement of atoms in space.  Classification of Isomers Structural or Stereo isomers Constitutional Structural (Constitutional) Isomers Skeletal Positional Functional Tutomers Tutomers Proton Valence Ring chain tautomerism Keto-Enol  Stereo Isomers Anomers Rotamers & Conformers Configurational Configurational Enantiomers Diastereomers Meso- Geometrical Geometrical Trans-isomer or Cis-isomers or Z-compounds E-compounds  Structural Isomers or constitutional isomers Compounds that have the same atoms present but differ in their order of connectivity. They have the same molecular formula but different structures.  Skeletal or Chain Isomers Compounds that have the same functional groups but differ in the length of the side chains. CH3 CH2 CH2 CH2 CH3 n- pentane CH 3 CH 3 CH 3 C CH 3 CH 3 C CH 2 CH 3 CH 3 H isopentane neopentane ORGANIC REACTION AND THEIR MECHANISMS 20 ◼  Breaking bonds Type of broken: Hemolytic fission: A:B A. + B. radicals 1.Heterolytic fission: + + - A:B A B ions 21 ◼  Indicating Steps in Mechanisms Curved arrows indicate breaking and forming of bonds Arrowheads with a “half” head (“fish-hook”) indicate homolytic and homogenic steps (called ‘radical processes’)—the motion of one electron Arrowheads with a complete head indicate heterolytic and heterogenic steps (called ‘polar processes’)—the motion of an electron pair ◼22 ◼Activation energy: minimum of potential energy that must be provided by collision of the reacting molecules for the reaction to occurs. ◼ Exothermic ◼ Endothermic ◼23 Classification of Organic Reactions 24 ◼  1- Acid-Base + - : : : : : : H-O: + H-Cl : H-O-H + :Cl : H H base acid conjugate acid conjugate base (accepts H+) (gives up H+) of H2O of HCl 25 ◼  2- Hydrolysis Reactions: In these type of reaction the bonds is broken by water. (e.g. hydrolysis of protein in presence of acids or enzymes to produce amino acids Water + Protein Amino acids 26 ◼  3-Reduction-oxidation (Redox) ❖ Oxidation: the reaction that involves the addition of oxygen. ❖ Reduction: the reaction that proceeds by the addition of hydrogen. 27 ◼ Types of Organic Reactions Substitution Elimination Addition Rearrangement ◼28  Substitution H H H H + KOH + KBr H Br H OH ◼Classification of organic reaction according to type of reactive intermediate involved: ◼ Free radical substitution reactions. ◼ Electrophilic substitution reactions SE ◼ Nucleophilic substitution reactions SN. 29 ◼ Classification of organic reaction according to the rate of reaction: Unimolecular nucleophilic substitution reaction SN1; The rate of reaction depends on the conc. of substrate only. Bimolecular nucleophilic substitution reactions SN2; The rate of reaction depends on the conc. of substrate and nucleophile. ◼Associ. Prof. Dr. A. Sh. El- 30 ◼ Etrawy Hydrocarbons  Classification of Hydrocarbons Alkanes Alkenes Arenes Alkynes (paraffins) (ofefins (aromatic) CnH2n+2 (acetylenes) CnH2n CnH2n-2 CnHn Nomenclature  Nomenclature of Alkanes Rules for naming compounds are given by the International Union for Pure and Applied Chemistry (IUPAC). Prefix----Parent----suffix Where are the substituents? How many carbons? What family?  Base Names Prefix Carbons I see much Meth- 1 memorization in Eth- 2 your future! Prop- 3 But- 4 Pent- 5 Hex- 6 Hept- 7 Oct- 8 Non- 9 Dec- 10  Alkanes First four members of the alkanes: Name # of C Condensed formula Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Butane 4 CH3CH2CH2CH3  Nomenclature of Alkanes 1. Find the longest continuous chain and use it as the parent name of the compound. CH2CH3 Named as a substituted hexane CH3CH2CH2CH CH3 CH3 CH2 Named as a substituted heptane H3C CH CHCH2CH3 CH2CH2CH3  Nomenclature of Alkanes 2. Beginning at the end nearer the first branch point, number each carbon atom in the longest chain you have found: CH3 CH3 1 7 NOT CH2 CH2 2 4 6 4 H3C CH CHCH2CH3 H3C CH CHCH2CH3 3 5 CH2CH2CH3 CH2CH2CH3 5 6 7 3 2 1  Nomenclature of Alkanes 3. Name and give the location of each substituent group. Note: Substituent groups are referred to as alkyl groups as well. CH3- methyl CH3CH2- ethyl CH3CH2CH2- propyl CH3CH2CH2CH2- butyl …etc.  Nomenclature of Alkanes CH3 1 CH2 2 4 H3C CH CHCH2CH3 3 CH2CH2CH3 5 6 7 Substituents: On C4, CH2CH3 (4-ethyl) On C3, CH3 (3-methyl)  Nomenclature of Alkanes 4. When two or more substituents are present, list them alphabetically. If two or more of the same substituent is present, number the constituents using a prefix: di (two) tri (three) tetra (four) ◼ n = normal: no branch at the end of the chain. ◼ Iso = indicates the presence of CH3 branch at the end of the chain. ◼ Neo = indicates the presence of 2CH3 branch at the end of the chain.  Structure and isomers of Alkanes Nos. of Molecular Name structure carbon formula C1 CH4 Methane H H C H H C2 C2H 6 Ethane CH3 CH3 C3 C3H 8 Propane CH3 CH2 CH3 Structure and isomers of Alkanes C4 C4H10 Butane CH 3 CH 2 CH 2 CH 3 n- butane CH 3 CH CH 3 CH 3 is obutane C5 C5H12 pentane CH3 CH2 CH2 CH2 CH3 n- pentane CH 3 CH 3 C CH 2 CH 3 H is opentane CH 3 CH 3 C CH 3 CH 3 neopentane  Classes of carbon and hydrogen: ◼ Primary carbon 1˚ry: indicates the presence of one carbon attached to the head carbon. ◼ Secondary carbon 2˚ry: indicates the presence of 2 carbons attached to the head carbon. ◼ Tertiary carbon 3˚ry: indicates the presence of 3 carbons attached to the head carbon. ◼ Quaternary carbon 4˚ry: Indicates the presence of four carbons attached to the head carbon. ◼ Hydrogen atoms are also referred to 1˚ry, 2˚ry or 3˚ry hydrogen according to the type of carbon they are bond  o  ry o 1 ry CH 3 CH 3 CH 3 CH C CH 2 CH 3 CH 3 o 3 ry o 4 ry Label the 1ºry, º2ry and 3ºry at indicated carbon atoms in the following compound CH3 H3C CH3 H3C OH 49  Draw all possible Isomers mention their type for the following MF C9H20 Step 1: Calculate Degree of unsaturation = (H2n+2 )- nos. H in M.formula / 2 = (2x9+2)- 20 = 20-20 = 0/2 = 0 CH3 H3C CH3 H3C nonane CH3 2-Methyloctane CH3 CH3 H3C CH3 H3C CH3 3-Methyloctane 4-Methyloctane CH3 CH3 H3C  CH3 CH3 CH3 C9H20 H3C CH3 H3C CH3 CH3 2,3-dimethylheptane 2,4-dimethylheptane CH3 CH3 CH3 H3C CH3 H3C CH3 CH3 2,6-dimethylheptane 2,5-dimethylheptane CH3 H3C H3C CH3 H3C H3C CH3 CH3 2,2-dimethylheptane 3,3-dimethylheptane  H3C CH3 H3C CH3 H3C CH3 H3C CH3 4,4-dimethylheptane 3,4-dimethylheptane H3C CH3 H3C CH3 H3C H3C H3C 3,5-dimethylheptane CH3 CH3 2,5-dimethylheptane CH3 CH3 H3C CH3 CH3 H3C CH3 2,3,4-trimethylhexane CH3  CH3 CH3 CH3 CH3 H3C H3C CH3 CH3 CH3 2,3,5-trimethylhexane H3C H3C 2,2,4-trimethylhexane CH3 H3C H3C CH3 CH3 CH3 H3C H3C CH3 2,2,3-trimethylhexane H3C 2,2,5-trimethylhexane CH3 CH3 H3C CH3 CH3 CH3 CH3 CH3 CH3 2,4,4-trimethylhexane 3,3,4-trimethylhexane  CH3 CH3 CH3 H3C CH3 H3C CH3 4-ethylheptane 3-ethyl-2-methylhexane H3C CH3 CH3 CH3 H3C CH3 H3C H3C CH3 3-ethyl-2-methylhexane CH3 3-ethyl-2,4-dimethylpentane H3C CH3 H3C CH3 3-ethyl-2,3-dimethylpentane  CH3 H3C H3C CH3 H3C CH3 H3C CH3 H3C CH3 CH3 H3C 2,2,3,3-tetramethylpentane 2,3,3,4-tetramethylpentane  It’s also easier to draw! Draw all possible Isomers and Mention their type & Give the IUPAC name for the following MF C6H14, C7H16 and C8H18 preparation  Preparation In industry from fractional distillation of petroleum and natural gas. In laboratory: by one of the following methods  From alkyl halides a) By reduction: using nascent hydrogen (Mg/Zn) and ethanol or zinc and acetic acid, or Li Al H4 can also be used since it is an excellent reducing agent: Br [H] CH3 CH2 CH CH3 CH3 CH2 CH2 CH3 + BrH b) via Grignard reagents: ether CH3 CH2 CH2 I + Mg CH3CH2CH2 Mg I H2 O CH3CH2CH3 + Mg (OH)2 c) Wurtz-reaction: 2R X + 2 Na ether R R + 2 NaX X= F, Cl, Br, I R = CH3, C2H5,.... From Alkene a) Catalytic hydrogenation of alkenes/ alkynes Syn addition of hydrogen Pt, Ni or Pd + H H pressure H H C C + 2 H H C C H H H H 1mol H2 1mol H2 Pt, Ni or Pd Pt, Ni or Pd C C C C pressure H H H H H H  b) via alkyl boranes to prepare long chain alkane alkylborane B2H6 Ag NO3 R - CH = CH2 2 (R - CH2 CH2)3 B NaOH 3 RCH2CH2 CH2 CH2 R From aldehyde or ketones: O R C H Zn HCl R CH 3 O Zn HCl R CH 2 R R C R [H] Zn Hg / HCl CH3 CH3CH2CH3 [H] Reduction C O H CH3 or NH2 NH2 OH CH3CH2CH3  From carboxylic Acids a) Decarboxylation: Soda lime CH3CH2 COOH CH3CH3 + Na2 CO3 NaOH + Ca O b) Kolbe’s electrolysis: At anode 2CH3 COO Na 2CH3 ‫ ـ‬+ CO2 + 2Na+ + 2e- 2CH3. CH3-CH3 Cathode reaction: 2Na+ + 2e- 2Na 2Na + H2O 2Na OH + H2  r your at fo te ks nt n ion Tha ! Th s an k ks a n T h