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Title: Thermodynamics
Description: thermodynamics=state function path function internal energy and entropy helmholts and gibbs function ideal gas equation thermodynamics 1 ,2,3 low
Description: thermodynamics=state function path function internal energy and entropy helmholts and gibbs function ideal gas equation thermodynamics 1 ,2,3 low
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MSc(Chem) Ist Sem
Dr Sanjeev Kumar Jha
Aromaticity in Benzenoid Compounds
In organic
chemistry, aromaticity is
a
property
of cyclic
(ring-
shaped), planar (flat) structures with a ring of resonance bonds that gives increased
stability compared to other geometric or connective arrangements with the same
set of atoms
...
Since the most common aromatic
compounds
are
derivatives
of benzene (an aromatic
hydrocarbon common
in petroleum and its distillates)
...
For resonance diagrams, the use of a double-headed arrow indicates that two
structures are not distinct entities but merely hypothetical possibilities
...
Criteria for Aromaticity:An aromatic (or aryl) compound contains a set of covalently bound atoms with
specific characteristics:
1
...
Coplanar structure, with all the contributing atoms in the same plane
3
...
A number of π delocalized electrons that is even, but not a multiple of 4
...
This is known
as Hückel's rule
...
Whereas benzene is aromatic (6 electrons, from 3 double
bonds), cyclobutadiene is antiaromatic, since the number of π delocalized electrons
is 4, which of course is a multiple of 4
...
An atom in an aromatic system can have other electrons
that are not part of the system, and are therefore ignored for the 4n + 2 rule
...
One lone pair is in the π system and
the other in the plane of the ring (analogous to the C–H bond in the other
positions)
...
Examples of benzenoid compounds
Title: Thermodynamics
Description: thermodynamics=state function path function internal energy and entropy helmholts and gibbs function ideal gas equation thermodynamics 1 ,2,3 low
Description: thermodynamics=state function path function internal energy and entropy helmholts and gibbs function ideal gas equation thermodynamics 1 ,2,3 low