Kolin Halidlerin (F, Cl, Br) Kimyasal Kaymalarının ve Titreşim Frekanslarının Teorik Çalışması

Abstract

Taban setleri 6-311++G(d,p) ve 6-31G(d,p) olan yoğunluk fonksiyon kuramı (B3LYP) yöntemi kullanılarak kolin halojenlerinin (F, Cl, Br), Gaussian 03 programında titreşim frekansları ve Paralel Quantum Solutions (PQS) programında ise, 1 H ve 13C çekirdeklerinin kimyasal kaymaları hesaplandı. Hesaplanan optimize geometrik yapı parametreleri, titreşim frekansları ve kimyasal kaymalar, deneysel verilerle çok iyi uyuşmaktadırlar. Kimyasal kaymalara ve titreşim frekanslarına, halojen katkılanmalarının, yani elektronegatifliğin etkileri incelendi. Kimyasal kaymaların, H çekirdeği için özellikle halojen atomuna en yakın çekirdekler olmak üzere azalırken, C çekirdeği için aynı sıralamayla arttığını gözledik. Halojenin elektronegatifliği ile kimyasal kaymanın kabaca çizgisel değişimi, C çekirdeği için ekranlanma ya da H çekirdeği için ekranlanmama ne olursa olsun, halojen atomu yakınındaki yerel elektron yoğunluğunun değişimin olarak yorumlandı.

Keywords

• Kolin halidleri
• titreşim spektroskopisi
• kimyasal kayma
• B3LYP
• Gaussian
• PQS

Theoretical Study of Vibrational Frequencies and Chemical Shifts of Choline Halides (F, Cl, Br)

Abstract

The vibrational frequencies and 1 H and 13C chemical shifts of choline halides have been calculated using density functional theory (B3LYP) method with 6-311++G(d, p) and 6-31 G(d, p) basis set level in Gaussian 03 and Parallel Quantum Solutions (PQS) ab initio packages programs, respectively. The calculated optimized geometric parameters, vibrational frequencies and chemical shifts were seen to be a very good agreement with the experimental data. The electronegativity influence of the halogen substitutions on the vibrational frequencies and chemical shifts have also been investigated. It was observed that the chemical shifts for H nucleus, especially the most near nucleus to the halogen atom decrease while it increases for C nucleus. The roughly linear variation of the chemical shift with the electronegativity of the halogen, whatever the shielding for C nucleus or deshielding for H nucleus is, has been commented that the local electron density near the halogen atom is affected.

Keywords

• Choline halides
• vibrational spectroscopy
• chemical shift
• B3LYP
• Gaussian
• PQS

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