کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1404661 | 1501920 | 2006 | 6 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Conformational analysis of 8-oxabicyclo[3.2.1]oct-6-en-3-one derivatives by NMR and theoretical calculations
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی آلی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Conformational analysis of 8-oxabicyclo[3.2.1]oct-6-en-3-one derivatives by NMR and theoretical calculations Conformational analysis of 8-oxabicyclo[3.2.1]oct-6-en-3-one derivatives by NMR and theoretical calculations](/preview/png/1404661.png)
چکیده انگلیسی
This work describes the conformational analysis of alcohols 2α,4α-dimethyl-6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3α-ol (5) and -3β-ol (6) and of alcohols 1,2α,4α,5-tetramethyl-6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3α-ol (7) and -3β-ol (8). Based on NMR data and AM1, HF/6-31G* and DFT/B3LYP/6-31G* geometry optimization, the pyran ring of compounds (5) to (7) is found to have a chair conformation. In the case of (8), NMR data indicate the presence of a boat conformer (8boat). However, the chair conformer (8chair) is predicted to have smaller relative energy as given by calculations employing different basis sets for either calculations on isolated molecules or including the solvent used in the NMR analyses (CDCl3). In contradistinction to thermodynamic results, DFT/B3LYP/6-31G* calculations of hydrogen (δH) and carbon (δC) chemical shifts of (8boat) were concordant with NMR experimental data of (8). Therefore, the chemical shift calculations agree better with the experimental results than does the quantum chemical calculations leading to the conformational analysis of (8).
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Structure - Volume 791, Issues 1â3, 19 June 2006, Pages 180-185
Journal: Journal of Molecular Structure - Volume 791, Issues 1â3, 19 June 2006, Pages 180-185
نویسندگان
Antônio Flávio C. Alcântara, Dorila Piló-Veloso, Wagner B. De Almeida, Célia R.A. Maltha, Luiz Cláudio A. Barbosa,