A Rapid and Innovative Method for the Identification of Aromatic and Anti-aromatic Nature of Organic...

Arijit Das, Suman Adhikari, Bijaya Paul, R. Sanjeev, V. Jagannadham

  Open Access OPEN ACCESS  Peer Reviewed PEER-REVIEWED

A Rapid and Innovative Method for the Identification of Aromatic and Anti-aromatic Nature of Organic Compounds

Arijit Das1,, Suman Adhikari1, Bijaya Paul2, R. Sanjeev3, V. Jagannadham4

1Department of Chemistry, Govt. Degree College, Dharmanagar, Tripura(N), India

2Department of Chemistry, Tripura University, Suryamaninagar, Tripura(W), India

3Department of Chemistry, Avanthi Degree and PG College, Hyderabad, India

4Department of Chemistry, Osmania University, Hyderabad, India.

Abstract

Prediction of aromatic and anti-aromatic behavior of organic compounds is a vitally important tool for students of chemistry at graduate and post-graduate level for solving different kinds of problems regarding reactivity, stability and acidic properties etc. In this manuscript we try to present a simple and innovative method for easy identification of aromatic and anti-aromatic behavior of organic compounds from their non-aromatic nature excluding Huckel’s rule of aromaticity.

Cite this article:

  • Das, Arijit, et al. "A Rapid and Innovative Method for the Identification of Aromatic and Anti-aromatic Nature of Organic Compounds." World Journal of Chemical Education 1.1 (2013): 6-8.
  • Das, A. , Adhikari, S. , Paul, B. , Sanjeev, R. , & Jagannadham, V. (2013). A Rapid and Innovative Method for the Identification of Aromatic and Anti-aromatic Nature of Organic Compounds. World Journal of Chemical Education, 1(1), 6-8.
  • Das, Arijit, Suman Adhikari, Bijaya Paul, R. Sanjeev, and V. Jagannadham. "A Rapid and Innovative Method for the Identification of Aromatic and Anti-aromatic Nature of Organic Compounds." World Journal of Chemical Education 1, no. 1 (2013): 6-8.

Import into BibTeX Import into EndNote Import into RefMan Import into RefWorks

1. Introduction

The method which is generally used [1, 2, 3, 4] for the prediction of aromatic and anti-aromatic nature of organic compounds based on Huckel’s rule of aromaticity is time consuming and confusing. Keeping this in view, an innovative method is necessary for the identification of aromatic and anti-aromatic nature of organic compounds from their non-aromatic nature.

Earlier seven new innovative methods including ten new formulae are introduced on the easy prediction of ‘Bond-Order of mono and diatomic homo and heteronuclear molecules or ions’, ‘Bond-order of oxide based acid radicals’, ‘Hybridization’, ‘IUPAC nomenclature of spiro and bicyclo compounds, ‘spin multiplicity value calculation and prediction of magnetic properties of diatomic hetero nuclear molecules and ions [5, 6, 7, 8, 9].

The present study will be a new innovative method involving two formulae by just manipulating the no of π bonds within the ring system and delocalized electron pair (excluding π electron pair within the ring system) with one (01). It would go a long way to help the students of organic chemistry who would choose the subject as their carrier. Experiment in vitro on 100 number of students show that the prediction of aromatic and anti-aromatic behavior of different kinds of organic compounds using Huckel’s rule, strike rate is 1Q/3min and by using these new innovative methods strike rate is 1Q/30secs.

On the basis of this, we can strongly suggest that by using this method the students can identify the aromatic and anti-aromatic nature of different kinds of organic compounds from their non-aromatic nature in a very short interval of time.

2. Discussion

2.1. Prediction of Aromatic Behavior

In the first case, the compound must be cyclic, planar (i.e. all the carbon atoms having same state of hybridization) with even number of A value, where [A = πb + e-p + 1 (constant)], here πb = number of π bonds with in the ring system and e-p = number of electron pair outside or adjacent to the ring system i.e. if the ring contains hetero atoms (atoms containing lone pair of electrons) which can undergo delocalization and each negative charge if present may be treated as one pair of electrons.

If the value of ‘A’, for a certain organic compound comes out as even number then this compound will be treated as aromatic compound.

2.2. Prediction of Anti-aromatic Behavior

In the second case, the compound must be cyclic, planar (i.e. all the carbon atoms having same state of hybridization) with odd number of A value, where [A = πb + e-p + 1(constant)], here πb = number of π bonds with in the ring system and e-p = number of electron pair outside or adjacent to the ring system i.e. if the ring contains hetero atoms which can undergo delocalization and each negative charge if present, may be treated as one pair of electrons.

If the value of ‘A’, for a certain organic compound comes out as odd number then this compound will treat as anti-aromatic compound.

2.3. In General Condition for Non-aromatic Behavior of Organic Compounds

Any compound that lacks one or more of the above features i.e. it may be acyclic / non-planar, is to be treated as non aromatic. But in this case, ‘A’ value may be even or odd number.

It is always to be noted that if the ring contains hetero atom like N, O, S etc, in this case we must count that electron pair in the evaluation of ‘A’ value which can undergo delocalization. We never count localized electron pair.

Examples are presented in Table 1.

Table 1. (Aromatic, anti-aromatic and non-aromatic nature of organic compounds by calculating A value)

There are some compounds which do not follow the above rule. Huckel’s also cannot explain the aromatic or non aromatic behavior of these compounds. These compounds are represented in the Table 2.

Table 2. (Omission behavior of aromatic and non aromatic organic compounds)

If we easily predict the nature of organic compound i.e. aromatic, anti aromatic or non aromatic then we can resolve different kind of problems regarding stability, reactivity, acidity etc. by using the following supposition.

1) Order of stability is aromatic > non aromatic > anti aromatic

2. Order of reactivity just follows the reverse order of stability as follows:

Anti-aromatic > non aromatic > aromatic

3. Acidity: Stability of Conjugate base α acidity

Eg: cyclopentadienyl anion(aromatic) > cyclopentadiene (non-aromatic) > cyclopentadienyl cation (anti aromatic). Hence, cyclopentadiene (its conjugate base i.e. Cyclopentadienyl anion is aromatic in nature) is much more acidic than cycloheptatriene (its conjugate base i.e. Cycloheptatrienyl anion is anti-aromatic in nature).

3. Conclusions

In conclusion here we approach a new innovative method for easy identification of aromatic, non aromatic and anti aromatic behavior of organic compounds with in very short time. This new method is very helpful to Undergraduate, Graduate and also in Postgraduate level students of chemistry. By using these methods we can easily predict nature of organic compounds in a very simple way.

Acknowledgement

The corresponding author, Dr. Arijit Das would be grateful to Dr. S. Rakshit, Principal, , Dharmanagar, Tripura(N), , for giving the opportunity to carry out the research work. Finally, Dr. Arijit Das would also be grateful to his own student’s group namely Mr. Debapriya Pal, Mr. Sudhabindu Das, Mr. Jayabrata Majumder, Kailashahar, Unakoti Tripura Mr. Abhishek Acharjee, Mr. Prajjal Das, Agartala, West Tripura and Mr. Jagatjyoti Chakroborty, Dharmanagar, , for their valuable sustaining mentality in this regard.

References

[1]  Finar I.L., Organic Chemistry, 6th Ed, Vol-1, p577-580, 2004.
In article      
 
[2]  Morrison R.T. and Boyd R.N., Organic Chemistry, 6th Ed, p504-507, 2008.
In article      
 
[3]  Solomons and Fryhle, Organic Chemistry, 8th Ed, p632-p639, 2009.
In article      
 
[4]  Smith J.G., Organic chemistry, 2nd edition, p616-619, 2008.
In article      
 
[5]  Das Arijit, New Innovative methods for prediction of Bond order of mono and diatomic molecules, ions and also acid radicals in a very short time’,‘Ind. J. of Applied Research’,03(07), p114, 2013.
In article      
 
[6]  Das Arijit, New Innovative Methods for Prediction of Hybridization State in a Very Short Time’, ‘Ind. J. of Applied Research’, 03(07), p594, 2013.
In article      
 
[7]  Das Arijit, New Innovative Methods for IUPAC Nomenclature of Bicyclo and Spiro Compounds in Organic Chemistry’,‘Ind. J. of Applied Research’, 03 (07), p596, 2013.
In article      
 
[8]  Das Arijit, ‘New Innovative Methods for Determination of Spin Multiplicity, Spin State and Magnetic Properties of Diatomic Hetero Nuclear Molecules or Ions in a Very Short Interval of Time’, ‘Ind. J .of Applied Research’, 03 (08), p67, 2013.
In article      
 
[9]  Das Arijit, New Innovative methods for prediction of Bond order of mono and diatomic molecules or ions having total number of (1-20)es in a very short time’, Ind. J. of Applied Research’,03(09),2013 (in press).
In article      
 
comments powered by Disqus
  • CiteULikeCiteULike
  • MendeleyMendeley
  • StumbleUponStumbleUpon
  • Add to DeliciousDelicious
  • FacebookFacebook
  • TwitterTwitter
  • LinkedInLinkedIn