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.