New Mansoura University Organic Chemistry Lecture 4 PDF

New Mansoura University Faculty of Science. _____________________________________________________________________ Organic Chemistry (CHE111) Lecture 4 Prepared By : Dr :Mohamed Ramadan  Lect...

New Mansoura University Faculty of Science. _____________________________________________________________________ Organic Chemistry (CHE111) Lecture 4 Prepared By : Dr :Mohamed Ramadan  Lecture Outlines. Preparation of alkanes, Reaction of alkanes, 1 alkenes, and alkynes 2 alkenes, and alkynes 3 Cycloalkanes 3 conformers  2- By the reduction of aldehydes and ketones: One method for converting carbonyl group to methylene group is the Clemmensen reduction. It involves the use of zinc amalgam (Zn-Hg) in the presence of concentrated hydrochloric acid.  3- By the hydrolysis of the alkylmagnesium halide: (Grignard 's reagents) Complete the following: H2O  Reactions of Alkanes They are quite non-reactive toward most reagent (Why?) 1-Non-polar compounds 2-Contain only strong sigma bonds. 1) Combustion Reactions of Alkanes At a high temperature, alkanes react vigorously and exothermically with oxygen. Basis for use as fuels. 2C4H10 (g ) + 13O2 (g ) → 8CO2 (g ) + 10H2O(g )  2) Substitution Reactions of Alkanes Primarily where halogen atoms replace hydrogen atoms (free radical reactions) CH4 + Cl2 ⎯⎯→ hv CH3Cl + HCl CH3Cl + Cl2 ⎯⎯→ hv CH2Cl2 + HCl CH2Cl2 + Cl2 ⎯⎯→ hv CHCl3 + HCl CHCl3 + Cl2 ⎯⎯→ hv CCl4 + HCl Cyclic Alkanes  Cycloalkanes have molecular formula CnH2n and contain carbon atoms arranged in a ring. Simple cycloalkanes are named by adding the prefix cyclo- to the name of the acyclic alkane having the same number of carbons. The Chair and Boat Forms of Cyclohexane Copyright © Cengage Learning. All rights reserved 14  Alkenes Properties, synthesis and chemical reactions Stereoisomers: Geometric Isomers- Cis-trans Nomenclature MF: C2H2Cl2 (Z) (E) Geometric Isomers- Cis-trans Nomenclature  General methods of preparation of alkenes: → H is removed from the β carbon, so it is called β-elimination Acid-base catalyzed reaction Major Minor Exercise  General reactions of alkenes. 1. Hydrogenation of Alkenes (reduction, addition of hydrogen) 2. Addition of halogen (X2) to alkenes: 3. Addition of water to Alkenes (giving alcohol): Orientation of Electrophilic Addition: Markovnikov’s Rule 4- Addition of hydrogen halides (H-X) to alkenes: Alkynes compounds and their chemical reactions  Synthesis: ❖ In general, chlorine or bromine is used with an inert halogenated solvent like chloromethane to create a vicinal dihalide from an alkene. ❖ The vicinal dihalide formed is then reacted with a strong base and heated to produce an alkyne. The two-step reaction pathway is shown: Reaction of alkynes Na or Li /  Does anyone have any questions? Thank you! CREDITS: This presentation template Slidesgo was created by Slidesgo, including Flaticon icons by Flaticon, and infographics & Freepik images by Freepik Please keep this slide for attribution