### Abstract

CNDO/2 calculations have been carried out on the protonation of some 4H-pyrido-(1,2-a)pyrimidine-4-one derivatives of biological interest. The calculated gas-phase protonation energy and the molecular electrostatic potential at the site of the protonation correlate satisfactorily with the experimentally determined basicity (pK_{a}) measured in aqueous solution. Making use of our linear regression equation obtained between the protonation energy and pK_{a} we estimated the pK_{a} value of a new derivative prior to experiment. The solvent effect on the basicity of compounds has been studied using the supermolecule approach. Calculated energy changes even for a simple monohydrated form make possible reasonable interpretation of a somewhat anomalous pK_{a} value of the 9-CH_{3} derivative found experimentally.

Original language | English |
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Pages (from-to) | 59-66 |

Number of pages | 8 |

Journal | Journal of Molecular Structure: THEOCHEM |

Volume | 153 |

Issue number | 1-2 |

DOIs | |

Publication status | Published - 1987 |

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### ASJC Scopus subject areas

- Physical and Theoretical Chemistry
- Computational Theory and Mathematics
- Atomic and Molecular Physics, and Optics

### Cite this

*Journal of Molecular Structure: THEOCHEM*,

*153*(1-2), 59-66. https://doi.org/10.1016/0166-1280(87)85003-0

**Semiempirical quantum-chemical calculations on the protonation of some N-bridgehead heterocycles.** / Nagy, P.; Hankó-Novák, K.; Szász, G.

Research output: Contribution to journal › Article

*Journal of Molecular Structure: THEOCHEM*, vol. 153, no. 1-2, pp. 59-66. https://doi.org/10.1016/0166-1280(87)85003-0

}

TY - JOUR

T1 - Semiempirical quantum-chemical calculations on the protonation of some N-bridgehead heterocycles

AU - Nagy, P.

AU - Hankó-Novák, K.

AU - Szász, G.

PY - 1987

Y1 - 1987

N2 - CNDO/2 calculations have been carried out on the protonation of some 4H-pyrido-(1,2-a)pyrimidine-4-one derivatives of biological interest. The calculated gas-phase protonation energy and the molecular electrostatic potential at the site of the protonation correlate satisfactorily with the experimentally determined basicity (pKa) measured in aqueous solution. Making use of our linear regression equation obtained between the protonation energy and pKa we estimated the pKa value of a new derivative prior to experiment. The solvent effect on the basicity of compounds has been studied using the supermolecule approach. Calculated energy changes even for a simple monohydrated form make possible reasonable interpretation of a somewhat anomalous pKa value of the 9-CH3 derivative found experimentally.

AB - CNDO/2 calculations have been carried out on the protonation of some 4H-pyrido-(1,2-a)pyrimidine-4-one derivatives of biological interest. The calculated gas-phase protonation energy and the molecular electrostatic potential at the site of the protonation correlate satisfactorily with the experimentally determined basicity (pKa) measured in aqueous solution. Making use of our linear regression equation obtained between the protonation energy and pKa we estimated the pKa value of a new derivative prior to experiment. The solvent effect on the basicity of compounds has been studied using the supermolecule approach. Calculated energy changes even for a simple monohydrated form make possible reasonable interpretation of a somewhat anomalous pKa value of the 9-CH3 derivative found experimentally.

UR - http://www.scopus.com/inward/record.url?scp=28544439672&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=28544439672&partnerID=8YFLogxK

U2 - 10.1016/0166-1280(87)85003-0

DO - 10.1016/0166-1280(87)85003-0

M3 - Article

AN - SCOPUS:28544439672

VL - 153

SP - 59

EP - 66

JO - Computational and Theoretical Chemistry

JF - Computational and Theoretical Chemistry

SN - 2210-271X

IS - 1-2

ER -