Tautomerism and Enols - July Dec Revision

Tautomerism

Tautomerism may be defined as the phenomenon in which a single compound exists in two readily interconvertible structures that differ markedly in the relative position of at least one atomic nucleus, generally hydrogen. The two different structures are known as tautomers of each other.

In the presence of acid or base, ketone or aldehyde with α-hydrogen is converted into hydroxyl ene (called enol), hence this type of isomerism in which keto and enol forms exist in dynamic equilibrium is also called ket-enol isomerism.


Enols

Preparation of aldehydes and ketones from alkynes

Hydration of alkynes in the presence of dilute sulphuric acid and HgSO4 as catalyst gives aldehydes and ketones.

Water adds to alkynes to form unstable enol intermediates which rearrange to form aldehydes or ketones.

Hydration of acetylene gives acetaldehyde.

Hydration of alkynes other than acetylene gives ketones.




Addition of water to alkynes (hydration of alkynes)

In the presence of acid (H2SO4) and HgSO-4, a molecule of water adds to the triple bond at 348K. The catalyst in this reaction is HgSO4 (Mercuric sulphate). The final products of this reaction are carbonyl compounds aldehydes and ketones.

Initially enol is formed which is raidly converted into an equilibrium mixture containing keto form in excess. Enol is so called because it contains 'ene' (double bond) and an alcoholic group (ol).



IIT JEE Revision - Acid Catalysed Hydration of Alkynes
In the presence of acid (H2SO4) and HgSO-4, a molecule of water adds to the triple bond at 348K.

The catalyst in this reaction is HgSO4 (Mercuric sulphate).

The final products of this reaction are carbonyl compounds aldehydes and ketones.

Initially enol is formed which is raidly converted into an equilibrium mixture containing keto form in excess.

Enol is so called because it contains 'ene' (double bond) and an alcoholic group (ol).

Example:
Addition of water to Ethyne or acytelene: Acetylene is passed into water (at about 330K) containing 60% H2SO4 and about 1% mercuric sulphate (HgSO4) as a catalyst, acetaldehyde is formed.

In the first step 'ethenol' is formed and in the second step the rearrangement of it takes place and its isomer 'acetaldehyde' is formed.

The conversion of enol form into keto form is termed tautomerism

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Morrison and Boyd Organic Chemistry

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Morrison and Boyd - Organic Chemistry - Slides - Notes II

Topics covered

Infrared Spectroscopy

Nuclear Magnetic Resonance

Spectrocopy Tables (IR & nmr)

Aldehydes & Ketones I

Aldehydes & Ketones II

Carboxylic Acids

Functional Derivatives of Carboxylic Acids

Carbanions I

Carbanions II

a,b-Unsaturated Carbonyls

notes on exam II

Amines, Syntheses

Amines, Reactions

Diazonium Salts

Phenols

Aryl Halides

Molecular Orbitals and Conservation of Symmetry

Polynuclear Aromatics

Heterocyclics

Carbohydrates

Fischer Proof of the Structure of (+)-glucose



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Morrison - Boyd Organic Chemistry Slides Notes

CHE-310/311 Organic Chemistry I


Available for topics





Introductory notes and review of general chemistry

Methane

Homework #6

Alkanes

Stereochemistry

Problem sets on the web for the R/S system of specification of configuration

Alkyl halides

Alcohols

Ethers

Alkenes,syntheses

Alkenes,reactions

Stereospecific and stereoselective reactions

Supplemental homework

Problem sets on the web regarding stereoselective/stereospecific reactions

Dienes

Alkynes

Exam III

Alicyclics

Aromaticity/benzene

Electrophilic Aromatic Substitution

Problem sets on the web involving electrophilic substitution reactions

Arenes



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Organic Chemistry Chapter 5 Stereochemistry: Chiral Molecules

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Solomon Org. Chemistry Chapter 4 Alkanes and Cycloalkanes: Conformations of Molecules

Chapter Outline

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Nomenclature and Physical Properties of Alcohols and Ethers

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Solomon Organic Chemistry Ch. 3 Acids and Bases in Organic Chemistry

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Solomon Organic Chemistry Chapter 2 Representative Carbon Compounds

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Solomon Org Chemistry Chapter 1 Carbon Compounds and Chemical Bonds

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Web Links for Solomons book on Organic Chemistry

Web Links for Solomons book on Organic Chemistry


These web links, organized by chapter, provide more information about topics covered in the text and will help in your study of organic chemistry.



http://www.wiley.com/college/chem/solomons190950/weblinks.html

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Presentation - Chiral Atoms

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Chiral Molecules - July Dec Revision

Chiral molecules

A molecule is said to be chiral if it lacks symmetry and its mirror images are not superimposable. To be chiral a molecule must lack symmetry, that is, a chiral molecule can not have any type or symmetry.

Carbon atoms with four sp3 hybridized orbitals can enter into up to four different bonds about the central carbon atom.
When the central carbon bonds with differing atoms or groups of atoms the carbon is termed an asymmetric carbon atom.

Bromochlorofluoromethane is an example of such a molecule. The central carbon, with four sp3 bonds oriented (pointing) to the corners of a tetrahedron, is bonded to a bromine, chlorine, fluorine and methane atoms. There is no symmetry to this molecule.

To explain things in a more simple way, Chiral molecules are like right hand left hand. Both hands have identical fingers but in different orientations. The little finger is in clockwise direction from the middle finger in right hand, where as the little is in the counterclockwise direction in the left hand. So you can fix a right hand to another person's left wrist. Right hand and left hand are different even though all the five diffetent fingers are more or less similar in both the hands.


Enantiomers are optical isomers. A chiral molecule will have enantiomers.


A solution in which both enantiomers of a compound are present in equal amounts is called a racemic mixture, or racemate.

Fluid - July Dec revision

There is continuity between the gaseous and liquid state. The term fluid is used for either liquid or a gas to recognize this continuity. A liquid can be viewed as a very dense gas. Liquid and gas can be distinguished only when the fluid is below its critical temperature and its pressure and volume lie under the dome (in isotherm) since in that situation liquid and gas are in equilibrium and a surface separating the two phases is visible.


Chapter: States of Matter




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