ASPIRANTSHUB.IN

                               DARE TO STAND OUT OF THE CROWD                      
Bookmark and Share


The planarity of the ring and the presence of conjugation in the ring are the primary requirement for a compound to be aromatic. The compound will be aromatic only if it satisfies the Huckels Rule. goHuckels rule states that a cyclic unsaturated compound containing (4n + 2)π  electrons which are conjugated, will have a special stability which is called-aromaticity. In the formula, n is an integer such as 0, 1,, 2, 3...etc. and it is called Huckel number.


The Huckels rule can be applied to molecules as Follows  :-

1)Cyclohexadiene                                                                                                    

In this number of π electron = 2 x 2 = 4

Hence does not satisfy Huckels rule for any value of n.Compound is not aromatic .


2) Benzene

In Benzene number of  π electron = 3 x 2 = 6 Satisfies Huckel's rule for n = 1 ,i.e. 4n+ 2 = 4 x1+2 = 6 ,Benzene is aromatic 


Resonance Energy:-

The resonance or delocatization of electrons cause stabilization and  the resonance hybrid is more stable than any resonance structures.Resonance energy is defined as a the difference in energy between the resonance hybrid of the species and the most stable resonance structures. It is the measure of extent of stabaization due to resonance. Resonance energy can be calculated in terms of heat of hydrogenation or heat of combustion.

The heats of hydrogenation and combustion of a compound is reduced due to resonance. Therefore the resonance energy is the difference between the expected and the observed values of heat of hydrogentation or heat of combustion.

 



Heat of hydrogenation is the amount of heat evolved when one mole of an unsaturated compound is completely hydrogenated.

 




Heat of combustion is the amount of heat evolved when one mole of an organic compound is completely burnt in excess of oxygen or air.

 



Check out some of the questions asked Recently by the students

>>Aromaticity

----------------------

>>Huckels Rule, Resonance Energy

----------------------

>>Aromatic compounds

----------------------

>>Benzenoid Hydrocarbons     ----------------------

>>Non Benzenoid Hydrocarbons

----------------------

>>Anti-Aromaticity

----------------------

>>Anti-Aromatic compounds

----------------------

 

If you have anything to ask us
then please post your querry right below and get it solved within 1 day.

  • sarah 3 days ago
  • do u think spending four hour per day for 8months can do all for entrance?if yes out of that how much time we should spend for biology physics and chemistry
  •  
  • experts;-
  • @sarah for physics and chemistry you need to mainly understand concepts and formulas but for biology you need to learn everything, so 90 minutes reading of trueman and then attempting questions from objective book should be ideal.
  • so, i can say 90 minutes for biology and 90 minutes for physics and chemistry per day on average.
  • amit kumar  3 days ago
  • How to prepare for organic chemistry

  • Expert;-
  • @ Amit kumar
  • Organic Chemistry can be a difficult part for some students but you can still prepare it. In organic chemistry you need to the basic mechanisms like induction effects, stability, Order of Acidity. You need to learn the various reactions of Alcohol, amines and their tests.
  • There are some common questions which usually comes in Entrance exams, so you need to practice sample papers and try to understand each part. You can gave 1Hr each day and you will be fine.
  •  

   (c) 2013-2014. Aspirantshub.in.  All Rights Reserved.