A theoretical study of substituted acetaldehyde, Keto-Enol System

مقدم أطروحة جامعية

al-Halasa, Wasim Fajr

مشرف أطروحة جامعية

Khalil, Salim Muhammad

أعضاء اللجنة

al-Umari, Hamzah
Qutaytat, Muhammad Ibrahim

الجامعة

جامعة مؤتة

الكلية

كلية العلوم

القسم الأكاديمي

قسم الكيمياء

دولة الجامعة

الأردن

الدرجة العلمية

ماجستير

تاريخ الدرجة العلمية

2002

الملخص الإنجليزي

MINDO-Forces method was used to calculate the optimized geometries, heats of formation, electron densities, entropies, orbital energies (HOMO-LUMO) and dipole moments of X-substituted acetaldehydes and their corresponding Enols (where X = H, F, O", OH, CN, NC, NH2, N02, CH3, CF3 and OCH3).

Also MNDO method was used to calculate thermodynamic functions (AG, AS).

The substituent affects the geometrical parameters (bond lengths and bond angles) especially at the position where the substituent is attached.

It was also found that the substituent affects the orbital energies, electron density distribution, and dipole moments.

The stabilizing effect of substituents on acetaldehydes and their enol counterparts was determined by Gibbs free energy and isoseismic reactions. It was found that the calculated heat of formation of acetaldehyde is less than that of its Enol, which indicates that the aldehyde is more stable than the Enol.

This is in agreement with the experimental results and theoretical calculations.

The present work is divided into two sections. Section one deals with the effect of substituents at oc-position and section two deals with the effect of substituents at carbonyl carbon-position. Section One : The effect of the substituents : as F, O", OH, CN, NC, NH2, N02, CH3, CF3 and OCH3 have been studied on oc-position of acetaldehydes and the Enol counterparts.

It was found that O", CN, NC, NH2, N02 and CF3 increase the stability of Enol while the others decrease the stability. We found that OH, OCH3, NH2, F, CH3, NC, CN and O" all behaved as electron releasing groups on Ketone, and it is more pronounced in the case of 0 \ while N02 and CF3 behaved as a strong electron withdrawing groups. In the case of enol, it was found that F, O", OH, NH2, and OCH3 behaved as electron releasing groups, and that is more pronounced in the case of O".

CN, NC, CH3, behaved as electron withdrawing groups and that is well obvious markedly in the case of N02 and CF3 where they behaved as a strong electron withdrawing group. Section Two : The effect of the substituents such as F, O", OH, CN, NC, NH2, N02, CH3, CF3 and OCH3 have been studied on carbonyl carbon -position of acetaldehydes and the Enol counterparts.

It was found that all substituents, except O", stabilized the ketone. In the case of the Ketone we found that N02 and CF3 behaved as strong electron withdrawing groups, while CN, NC and CH3 behaved as weak electron withdrawing groups.

The rest of the substituents behaved as electron releasing groups. In the case of the Enol we found that NO2 and CF3 behaved as strong electron withdrawing groups, while CN, NC and CH3 behaved as a weak electron releasing groups, the rest of the substituents behaved as electron releasing groups. *From this study it is found that: i- CN, NC and CH3 showed amphielectronic behavior where they behaved as electron releasing and electron withdrawing groups depending on the electron demand. *ii-all substituents stabilized the ketone except O" in the case of carbonyl carbon-position, while in the case of a-position some of the substituents stabilized the Ketone while the others destabilized it.

التخصصات الرئيسية

الكيمياء

الموضوعات

• المركبات العضوية
• أسيتالدهيد

عدد الصفحات

119

قائمة المحتويات

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-310422