Chemistry of Alkenes and Criminal Evidence

Chemistry and Criminal Evidence

• Course focused on chemistry and its relation to criminal evidence.
• The course is part of Chemistry program at Mansoura University.

Basic Principles of Organic Chemistry

• Lecture 3 focused on organic chemistry, likely the structure and classifications of alkenes.

Alkenes

• Alkenes are hydrocarbons with at least one carbon-carbon double bond.
• General formula: C_nH_2n
• IUPAC nomenclature is used to name alkenes.
• The longest carbon chain containing the double bond is chosen.
• The double bond is numbered to give the lowest possible number.
• Multiple double bonds are indicated by prefixes like "di," "tri," etc.

Examples of Alkenes

• Examples of named alkenes are provided in the slides, like
• Ethene, Propene, 1-Butene, 2-Butene, and others.
• Alkenes isomers (cis/ trans isomers) are differentiated by configuration around the double bond.
• Further classifications of isomers like alkenes were discussed for different cases.

Common System

• Alkyl and alkenyl groups, like vinyl and allyl, were defined and examples were provided.
• Naming conventions for cyclic alkenes are also included.

Geometrical Isomerism

• Geometrical isomers differ in the arrangement of atoms around the double bond.
• "Cis" and "trans" isomers of 2-Butene were provided as a notable example.
• Different groups around the double bond are evaluated for priority based on atomic weight.

Preparation of Alkenes

• Alkenes can be prepared by elimination reactions.
• Dehydrohalogenation of alkyl halides is a notable example where alkene is formed, often in presence of strong bases such as KOH.
• Saytzeff rule determines which hydrogen atoms are eliminated in elimination reactions to predict the most likely alkene product
• Dehydration of alcohols is another method.

Mechanism of Alkene Reactions

• Mechanisms of reactions like halogenation and dehydration of alcohols are described in slide 9 and 10 to show how they occur.
• Stability of carbocations and resonance in intermediates are important concepts.

Dehalogenation of Vicinal Dihalides

• A method involves using Mg and Zn to form alkenes.

Kolb Electrolysis

• A chemical process uses electricity to synthesize compounds; specific to forming alkynes.

Reduction of Alkynes

• Method by which alkynes are converted to alkenes/alkanes. Conditions involved (like catalysts) may be noted.

Oxidation Reactions

• Various reactions of alkenes with oxidative agents are discussed, including those with KMnO4 and OsO4, often resulting in glycol formation.
• Addition of oxygen using oxidative agents to yield alkene oxides is included.
• Oxidative cleavage methods involving double bond cleavage with alkaline KMnO4 or ozone are discussed, often yielding carboxylic acids as products.

Addition Reactions (Alkenes)

• Alkenes undergo various addition reactions, such as addition of hydrogen, halogens, hydrogen halides, and water, resulting in different products.
• Markovnikov's and anti-Markovnikov's addition reactions, along with peroxide effect, are explored.

Addition Reactions (Alkynes)

• Alkynes undergo similar addition reactions.
• Various addition reaction mechanisms are explored. Conditions like solvent and catalysts are noted.

Polymerization (Alkenes and Alkynes)

• Methods of linking monomers into polymers are explained. Notably, the formation of polyethylene from ethylene.
• Polymerization procedures for alkynes are noted.

Substitution Reactions (Propane)

• Examples of substitution reactions in propene. Notably, free radical halogenation.

Alkynes

• General formula: C_nH_2n-2
• Naming often follows IUPAC conventions.
• Longest chain containing the triple bond is prioritized; numbering is given for lowest position of the triple bond.
• Examples like Ethyne, Propyne are given.
• Isomers and common naming conventions are introduced.

Preparation of Alkynes

• Dehydrohalogenation of vicinal and geminal dihalides are methods for synthesizing alkynes.
• Alkynes can also be made from acetylene or calcium carbide

Reactions of Alkynes

• Various reactions of alkynes are explained. This includes halogenation, hydrogenation and addition of hydrogen halides, and other addition-type reactions.

Polymerization (of Alkynes and Alkenes)

• Formation of polymers by connecting monomers is described, involving alkene monomers.

This quiz explores the fascinating intersection of chemistry and criminal evidence, particularly focusing on alkenes. It covers key concepts about the structure, nomenclature, and examples of alkenes, along with their significance in criminal investigations. Ideal for students in the Chemistry program at Mansoura University.