Pharmaceutical Organic Chemistry I PC101 PDF

Pharmaceutical Organic Chemistry I PC101 Alkenes Mona S. El-Zoghbi, Ph. D. Pharm. Sc. Associate professor of pharmaceutical Chemistry Pharmaceutical Chemistry Department [email protected] Intended learning outc...

Pharmaceutical Organic Chemistry I PC101 Alkenes Mona S. El-Zoghbi, Ph. D. Pharm. Sc. Associate professor of pharmaceutical Chemistry Pharmaceutical Chemistry Department [email protected] Intended learning outcomes of the course (ILOs) On successful completion of the course, you should be able to: ❖Recognize several organic terms. ❖Underline the different types of chemical bonds. ❖Recognize the different classes of organic compounds. ❖Assess the structural feature of organic compound and its IUPAC name. ❖Demonstrate alkanes, alkenes, alkynes and alkyl halides (nomenclature, physical and chemical properties, preparation and chemical reactions). ❖ Classify different reaction mechanism. ❖ Outline fundamental principles and applications of stereochemistry, stereo-dynamic, hydroxyl and carbonyl compounds. ❖ Identify the principles of aromaticity and benzenoid compounds.  Unsaturated Hydrocarbons I. Alkenes CnH2n carbon-carbon double bond sp2 hybridized with bond angle 120º Nomenclature of alkenes: I. I.U.P.A.C. Nomenclature: Select the longest continuous chain containing double bond. Name the chain according to number of carbon atoms and replace the suffix “-ane” by “-ene”. Number the chain and give the double bond the lowest possible number The substituents are named and their positions are indicated. eg. CH3 CH2 CH2 CH CH2 CH2 CH3 CH CH2 3-propyl-1-hexene CH3 eg. CH3 CH2 CH CH CH2 CH CH3 6-methyl-3-heptene II. Common or trivial names: Naming the common name of the corresponding alkane and we replace the suffix “-ane" with “-ylene”. CH2=CH2 "ethylene" CH3–CH=CH2 "propylene" CH3–CH2–CH=CH2 "α-butylene or 1-butylene" CH3–CH=CH–CH3 "β-butylene or 2-butylene" CH3 CH3 C CH2 "Isobutylene" As derivatives of ethylene: CH3–CH=CH2 "methylethylene" CH3–CH=CH–CH3 "sym.dimethyl ethylene”. CH3 CH2 C CH2 "Asym. diethylethylene." CH2 CH3 Unsaturated alkyl groups: Remove the letter “e” from alkene and replace it by “–yl” to be alkenyl The attachment is always number one The number indicates the position of the double bond -H CH2 CH2 CH2 CH "ethene" "ethenyl" or "vinyl" -H CH3 CH CH2 CH2 CH CH2 "Propene" "2-propenyl" or "allyl" -H CH3 CH CH "1-propenyl"  Unsaturated Hydrocarbons containing two or more double bonds. Compounds containing two double bonds "CnH2n–2" Compounds containing three double bonds "CnH2n–4". I.U.P.A.C. nomenclature: Select the longest continuous chain containing the maximum number of double bonds Name the chain according to number of carbon atoms and replace the suffix “-ane” by “-diene” if two double bonds and by “- triene” if three double bonds Number the chain giving the double bonds the lowest possible numbers. CH3 CH2 eg. CH3 C C CH2 C CH2 CH3 CH3 "2-Ethyl-4,5-dimethyl-1,4-hexadiene"  Preparation of alkenes: I. By reduction of alkynes: R R H2/Ni2 B or C C H2/Pd-CaCO3 H H syn addition R C C R "cis-alkene" Na or Li/NH3 R H trans addition C C H R "Trans-alkene" II. By Elimination Reactions: 1. From alkyl halides: “Dehydrohalogenation" H alcoholic KOH/ C C C C - HX X alc. KOH eg. CH3 CH2 CH CH3 CH3 CH CH CH3 + - HBr Br "major" CH3 CH2 CH CH2 "minor" The order of reactivity and hence the elimination of halogen iodine more than bromine more than chlorine more than fluorine tertiary alkyl halides are more reactive than secondary than primary Saytzeff's rule: The predominant alkene is the most substituted one  Saytzeff's rule: 2. From dihalides: "dehalogenation" Zn/HAc C C C C - X2 X X vicinal dihalide Zn/HAc CH3 CH CH CH3 CH3 CH CH CH3 - Br2 Br Br "2,3-Dibromobutane" "2-butene" 3. From alcohols: "Dehydration" Conc. H2SO4 C C C C + H2O 160 - 180oC H OH