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The Chemistry of Carbon

Organic chemistry is the branch of chemistry dealing with the compounds of carbon. While it is only the fourteenth most common element on earth, carbon forms by far the greatest number of different compounds. Organic chemistry is of vital importance to the petrochemical, pharmaceutical, and textile industries, where a prime concern is the synthesis of new organic molecules and polymers.

Bonding & Molecular Structure

Compounds containing only hydrogen and carbon, of which there are many thousands, are called hydrocarbons; the simplest is methane (CH4).


A particular type of organic compound, such as an alcohol, aldehyde, ether or ketone, is identified by the functional group of atoms. The functional group is the part of the molecule most responsible for its particular chemical nature.

Organic compounds containing nitrogen are important in biochemistry. They usually contain the amine group (NH2). Molecules containing both the NH2 and COOH groups are called amino acids and are the building blocks of proteins.  Without knowledge  these organic compounds, studying the structure and function of DNA would be a futile effort.


Constitutional isomers have the same molecular formula, such as C8H16, but differ in how the atoms are connected. Constitutional isomers have different numbers in their names or completely different names.

There are five isomers of hexane, C6H14

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hexane

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2-methylpentane

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3-methylpentane

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2,2-dimethylbutane

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2,3-dimethylbutane

 


Configurational isomers not only have the same molecular formula, but also the same atom connections. Their names are the same, including numbers for substituents. They differ only in prefixes such as cis, trans, endo, exo, (R), or (S).   Enantiomers and Diastereomers are configurational isomers.

Types of Isomer tree   http://www.chem.ucalgary.ca/courses/350/Carey/Ch07/ch7-1.html

Conformational isomers are identical in name because they cannot be separated, at least at room temperature, due to rapid interconversion. They are distinguished only by names such as axial, equatorial, chair, boat, eclipsed, and staggered. Only 3-D representations of compounds such as Fischer projections, Newman projections, and chair/boat depictions make distinctions between conformational isomers.


 


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STERIC STRAIN IN MONOSUBSTITUTED
CYCLOHEXANES
GROUP kJ/mol  kcal/mol 
-F  0.5 0.12 
-Cl 1.0  0.25
-Br  1.0 0.25
-OH  2.1 0.5
-CH3 3.8  0.9
-CH2CH3 4.0 0.95
-CH(CH3)2  4.6  1.1
-C(CH3)3 11.4  2.7
-C6H5 6.3  1.5
-COOH  2.9 0.7
-CN  0.4  0.1