Predicting the hybridization state: a comparative study between conventional and innovative formulae

Received Sep 11, 2019 Revised Nov 7, 2019 Accepted Jan 1, 2020 In previous published articles, formulae-based mnemonics by counting the total number of σ bonds with a lone pair of electrons (LP), a localized negative charge (LNC), or a localized lone pair of electrons (LLP) and subtracting one (01) from this total value (TSLP, TSLNC, or TSLLP) to predict the power of the hybridization state of simple molecules or ions and organic compounds, including heterocyclic compounds have been discussed. These are the innovative and time-efficient methods of enhancing student interest. Here, in this new article, the limitations of conventional formulae in comparison to the use of innovative formulae have been discussed along with the application of the hybridization state in different fields of chemical education. This article encourages students to solve multiple choice type questions (MCQs) at different competitive examinations in a time economic ground on the prediction of hybridization state of simple molecules or ions to know their normal and subnormal geometry and prediction of hybridization state of hetero atom in different heterocyclic compounds to know the planarity of the compounds, which is very essential factor for prediction of aromaticity of heterocyclic compounds. Educators can use this comparative study in their classroom lectures to make chemistry authentic and intriguing. Because the use of mnemonics in classroom lectures is an essential tool to become a distinguished educator.

Conventional formula for the prediction of hybridization state of simple molecules or ions and hetero atom in different heterocyclic compounds had wide limitations in the field of both organic and inorganic chemistry which were misguided by the educators since last 80-90 years. In this article, I have tried to focus the limitations of conventional formula to predict the hybridization state of center atom in simple molecules or ions and also in the organic compounds in and solved them in the light of innovative formulae.

RESULTS AND ANALYSIS 3.1. Comparative study between conventional and innovative formulae for the prediction of the hybridization state of different atoms in simple molecules or ions.
When using a conventional formula, it is not possible to predict the hybridization state of an O atom in the cyclic ozone, as illustrated in Figure 1 Example 1: The hybridization state of O in cyclic ozone It is not possible to predict the hybridization state of the S atom in S8 and the P atom in P4 using a conventional formula, as shown in Figure 2. It is not possible to predict the hybridization state of a terminal carbon atom in alkynes using a conventional formula.
Example 4: The hybridization state of Ethyne, as presented in Figure 3.  It is not possible to predict the hybridization state of oxygen atoms in the cyclic ozone or hydrogen peroxide, the S atom in S8, or the P atom in P4 using a conventional formula; however, using an innovative formula allows the hybridization state to be determined with absolute accuracy in all cases.

A comparative study between conventional and innovative formulae to predict the hybridization state of carbon atoms in different non-heterocyclic organic compounds
It is not possible to predict the hybridization state of carbon atoms in cyclopropene, cyclopentadiene, cycloheptatriene, cyclopropenyl anion, cyclopentadienyl anion, cycloheptatrienyl anion, cyclopropenyl cation, cyclopentadienyl cation, and cycloheptatrienyl cation, benzene, and toluene using a conventional formulae; however, using an innovative formula allows the hybridization state to be determined with absolute accuracy in all cases.
When a conventional formula was used the hybridization state of a vertex carbon atom in cycloalkenes, such as cyclopropene, cyclopentadiene, and cycloheptatriene, as shown in Figure 5, Figure 6, and Figure 7, it gave erroneous results.   The hybridization state of carbon atoms, other than vertex carbon, in cycloalkenes, such as cyclopropene, cyclopentadiene and cycloheptatriene, Figure 5, Figure 6, and Figure 7, was unpredictable when using a conventional formula. i) Conventional formula The power of the hybridization state of the rest carbons (P) = 1/2 (V+MA−C+A) = 1/2 (4+1-0) = 2.5 (unpredictable hybridization state). ii) Innovative formula The power of the hybridization state was (PHyb) = (TSLNC) -1 = 3-1 = 2 (sp 2 hybridization state of rest carbons other than vertex carbon).
The hybridization state of vertex carbon atoms bearing a negative charge in cycloalkenyl anions, such as cyclopropenyl anion, cyclopentadienyl anion, and cycloheptatrienyl anion, Figure 5, Figure 6, and The hybridization state of carbon atoms in benzene, toluene, and so on is unpredictable using a conventional formula but, when using an innovative formula, the hybridization state will be determined with absolute accuracy in all cases.
A carbon atom in benzene as illustrated in

A comparative study between conventional and innovative formulae to predict the hybridization state of a heteroatom in different heterocyclic compounds
It is not possible to predict the hybridization state of heteroatom nitrogen in pyridine, quinoline, isoquinoline, pyrimidine, thiazole, benzothiazole, pyrazine, cyanidine, phenazine, 1,2,3,4-tetrazine, azocine, azetine, and aziridine, or an oxygen atom in oxetan using a conventional formula. However, when using an innovative formula, the hybridization state of a heteroatom in nitrogen will be determined with absolute accuracy in all cases. i) Conventional formula The power of the hybridization state of a nitrogen atom in pyridine is P = 1/2 (V+MA−C+A) = 1/2 (5 + 0 -0 + 0) = 2.5 (unpredictable hybridization state) and the power of the hybridization state of a nitrogen atom in quinolone is P = 1/2 (V+H−C+A) = 1/2 (5 + 0 -0 + 0) = 2.5 (unpredictable hybridization state) illustrated in Figure 9.

Pyrrole
Pyridine Quinoline Figure 9. Structure of pyrrole, pyridine, and quinolone (sp 2 hybridization state of N atom) and the power of the hybridization state of a nitrogen atom in quinolone is PHyb = (3 -1) = 2 (σ bonds = 2 & LLP = 1) (sp 2 hybridization state of N atom) illustrated in Figure 9.

CONCLUSION
In this article, the limitations of conventional formulae have been discussed in the light of innovative formulae to predict the hybridization state of simple molecules or ions and organic compounds, including heterocyclic compounds. Educators can use this comparative study in their classroom lectures to make chemistry intriguing and trustworthy.