Organic Chemistry Lecture Notes 2024/2025 PDF

Faculty of Science Organic Chemistry CHE111 Lecture 5: Functional group and isomerism Prepared by: Assoc. Prof. Ahmed Ragab 2024/2025  Content 1. Classi...

Faculty of Science Organic Chemistry CHE111 Lecture 5: Functional group and isomerism Prepared by: Assoc. Prof. Ahmed Ragab 2024/2025  Content 1. Classification of organic compounds 2. Functional group of organic compounds 3. Types of chemical reaction 4. Isomerism Summarize the Functional group alkene Aromatic hydrocarbon Alkyne Alkyl halid Alcohols  Ether aldehyde Ketone Carboxylic acid Y= carboxylic acid OR = carboxylic ester derivatives X = acid halide NH2 or NHR or NR2 = amide Amine Nitrile Types of chemical reactions Types of chemical reactions (I) Homolytic and Heterolytic fission  Homolytic Fission ❑ In this process each of the atoms acquires one of the bonding two electrons. A B or A.. B A. +.B ❑ The products. A· and B· are called Fee Radicals. C C C + C light Cl Cl Cl + Cl or heat homolytic cleavage  Heterolytic Fission A B A + +..B- (1) -. + A B A. + B (2) The products of heterolytic fission are ions C + X C Carbocation X C + X Carboanion Types of reagents  Types of reagents Electrophilic reagents (electron love reagents) 1. Ions with positive charge SO3H+, NO2+, CH3+ 2. Neutral molecules as Lewis acids BF3 AlCl3 FeCl 3 SbCl 3 ZnCl2 HgCl2 3. Oxidizing agents (have ability to accept electrons) = poor in e-  Nucleophilic reagents (nucleus-loving reagents) 1. Negatively Charged Nucleophiles: HO ‫־‬, HS‫־‬, RO‫ ־‬, X‫־‬ 2. Neutral charge bearing with electron pairs : HOH, ROH, NH3 3. Reducing agents (have ability to donate electrons) = rich in e-  Remember types of reactive Intermediates Reactive Intermediates After heterolytic and homolytic cleavage a new species is obtained can be determined as reactive intermediates and are believed to be transient intermediates in many reactions. The general structures and names of four such intermediates are given below.  Types of chemical reactions Addition reaction the number of σ-bonds in the substrate molecule increases, usually at the expense of one or more π-bonds. Elimination reactions the number of σ-bonds in the substrate decreases, and new π-bonds are often forme.  Types of chemical reactions Substitution reactions are characterized by replacement of an atom or group (Y) by another atom or group (Z). Aside from these group, the number of bonds does not change. A rearrangement reaction generates an isomer, and again the number of bonds normally does not change. Hofmann Rearrangement Isomerism  What is Isomerism? Isomerism is the phenomenon in which more than one compounds have the same chemical formula, but different chemical structures. Isomers Chemical compounds that have identical chemical formulae but differ in properties and the arrangement of atoms in the molecule.  It is also known as skeletal isomerism. Chain The components of these isomers display differently branched structures. Isomerism Commonly, chain isomers differ in the branching of carbon An example of chain isomerism can be observed in the compound C5H12, as illustrated below.  Position Isomerism The positions of the functional groups or substituent atoms are different in position isomers. Typically, this isomerism involves the attachment of the functional groups to different carbon atoms in the carbon chain. An example of this type of isomerism can be observed in the compounds having the formula C3H7Cl. Draw the position isotherm  Functional Isomerism ❑ It is also known as functional group isomerism. ❑ As the name suggests, it refers to the compounds that have the same chemical formula but different functional groups attached to them. ❑ An example of functional isomerism can be observed in the compound C3H6O. Metamerism  Tautomerism Tautomerism is a phenomenon where a single chemical compound tends to exist in two or more interconvertible structures that are different in terms of the relative position of one atomic nucleus, which is generally hydrogen.  Ring-Chain Isomerism ❑ In ring-chain isomerism, one of the isomers has an open-chain structure whereas the other has a ring structure. ❑ They generally contain a different number of pi bonds. ❑ A great example of this type of isomerism can be observed in C3H6. Propene and cyclopropane are the resulting isomers, as illustrated below  Optical Isomerism * * * * Optical Isomerism are molecules that are non-superimposable mirror images of each other and they are not identical. Molecules with a chiral carbon show this kind of isomerism. Chiral carbons, also known as asymmetric carbons, refer to a carbon atom that is bonded to four different functional groups.