Organic Chemistry

Comparison of E1 and E2 Elimination Mechanisms – Let’s summarize the major points to remember about the E1 and E2 reactions, focusing on the factors that help us predict which of these mechanisms will operate under a given set of experimental conditions. Then we will organize these factors into a …

Stereochemistry of the E2 Reaction – In this subject Stereochemistry of the E2 Reaction will be discussed – Like the SN2 reaction, the E2 reaction follows a concerted mechanism: Bond breaking and bond formation take place at the same time, and the partial formation of new bonds lowers the energy …

Second-Order Elimination: The E2 Reaction – Eliminations can also take place under second-order conditions with a strong base present. – As an example, consider the reaction of tert-butyl bromide with methoxide ion in methanol. – This is a second-order reaction because methoxide ion is a strong base as well as …

Positional Orientation of Elimination: Zaitsev’s Rule – In this subject , Positional Orientation of Elimination: Zaitsev’s Rule will be discussed – Many compounds can eliminate in more than one way, to give mixtures of alkenes. – In many cases, we can predict which elimination product will predominate. – In the …

First-Order Elimination : The E1 Reaction – An elimination involves the loss of two atoms or groups from the substrate, usually with formation of a pi bond. – Elimination reactions frequently accompany and compete with substitutions. – By varying the reagents and conditions, we can often modify a reaction to …

Comparison of SN1 and SN2 Reactions Let’s compare what we know about the SN1 and SN2 Reactions and reactions, the organize this material into a brief table. (1) Effect of the Nucleophile on SN1 and SN2 Reactions – The nucleophile takes part in the slow step (the only step) of …

Rearrangements in the SN1 Reactions – Carbocations frequently undergo structural changes, called rearrangements, to form more stable ions. – A rearrangement may occur after a carbocation has formed or it may occur as the leaving group is leaving. – Rearrangements are not seen in SN2 reactions, where no carbocation is …

Stereochemistry of the SN1 Reaction – The SN2 reaction is stereospecific: the nucleophile attacks from the back side of the electrophilic carbon atom, giving inversion of configuration. – In contrast, the SN1 reaction is not stereospecific. – In the SN1 mechanism, the carbo-cation intermediate is sp2 hybridized and planar. – …

SN1 Reaction: First-Order Nucleophilic Substitution – When tert-butyl bromide is placed in boiling methanol, methyl tert butyl ether can be isolated from the reaction mixture. – Because this reaction takes place with the solvent acting as the nucleophile, it is called a solvolysis (solvo for “solvent,” plus lysis, meaning “cleavage”) …

Stereochemistry of the SN2 Reaction – As we have seen, the reaction SN2 requires attack by a nucleophile on the back side of an electrophilic carbon atom (see Figure) – A carbon atom can have only four filled bonding orbitals (an octet), so the leaving group must leave as the …

Reactivity of the Substrate in SN2 Reactions – We will often refer to the alkyl halide as the substrate: literally, the compound that is being attacked by the reagent. – Just as the nucleophile is important in the SN2 reaction, the structure of the alkyl halide is equally important. – …

Factors Affecting SN2 Reactions: Strength of the Nucleophile – we will discuss Factors Affecting SN2 Reactions especially Strength of the Nucleophile – We will use the SN2 reaction as an example of how we study the properties of the species that participate in the reaction. – Both the nucleophile and …

In this subject Second-Order Nucleophilic Substitution: The SN2 Reaction of Alkyl halides will be discussed Reactions of Alkyl Halides: Substitution and Elimination – Alkyl halides are easily converted to many other functional groups. – The halogen atom can leave with its bonding pair of electrons to form a stable halide …

Preparation of alkyl halides – Most Methods of preparation of alkyl halides exploit the chemistry of functional groups we have not yet covered. – For now, we review free-radical halogenation and only summarize other, often more useful, syntheses of alkyl halides. – The other Methods of preparation of alkyl halides …

Physical Properties of Alkyl Halides will be discussed such as dipole moment, London force, Dipole–dipole attractions, densities of common alkyl halides. Structure of Alkyl Halides – In an alkyl halide, the halogen atom is bonded to an carbon atom. – The halogen is more electronegative than carbon, and the bond …

Introduction to Alkyl Halides – In this subject , we consider Nomenclature of alkyl halides. – Our study of organic chemistry is organized into families of compounds classified by their functional groups. – We use alkyl halides to introduce substitution and elimination, two of the most important types of reactions …

Essential terms in Stereochemistry stereochemistry – stereochemistry is The study of the three-dimensional structure of molecules. – It is the systematic presentation of a specific field of science and technology that traditionally requires a short preliminary excursion into history. – Stereochemistry is the (chemistry of space). – In this subject …

Resolution of Enantiomers – Pure enantiomers of optically active compounds are often obtained by isolation from biological sources. – Most optically active molecules are found as only one enantiomer in living organisms. – For example, pure (+)-tartaric acid can be isolated from the precipitate formed by yeast during the fermentation …

What is Diastereomers? – We have defined stereoisomers as isomers whose atoms are bonded together in the same order but differ in how the atoms are directed in space. – We have also considered enantiomers (mirror-image isomers) in detail. – All other stereoisomers are classified as diastereomers, which are defined …

Meso Compounds – Compounds that are achiral even though they have asymmetric carbon atoms are called meso compounds. – The (2R,3S) isomer of 2,3-dibromobutane is a meso compound. – most meso compounds have this kind of symmetric structure, with two similar halves of the molecule having opposite configurations. – In …