Eylem Seç
Secondary deuterium isotope effects in the hydrolysis of some acetals
Başlık:
Secondary deuterium isotope effects in the hydrolysis of some acetals
Yazar:
Paterson, Robert Vincent, author.
ISBN:
9780438057425
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (172 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: B. Capon.
Özet:
Secondary alpha-deuterium kinetic isotope effects have been determined in the hydrolyses of some acetals. Benzaldehyde dimethyl acetal and 2-phenyl-1,3-dioiolan show isotope effects in agreement with an A1 mechanism, 2-Phenyl-4,4,5,5-tetramethy 1-1,3-dioxolan, which has been shown to undergo hydrolysis by an A2 type mechanism, has an isotope effect in agreement with participation by water in the transition state. Hydrolysis of benzylidene norbomanediols, although complicated by isomerisation, has an isotope effect in agreement with an A2 mechanism. Kinetic isotope effects in acetals which have a neighbouring carboxyl group have also been determined. Hydrolysis of 2-carboxybenzaldehyde dimethyl acetal in aqueous and 82% w/w dioxan-water buffers has isotope effects in agreement with a large degree of carbonium ion character in the transition state. Anderson and Capon proposed nucleophilic participation in the hydrolysis of this acetal in 82% dioxan-water. The isotope effect determined in this study is not in agreement with this finding. It is rationalised in terms of electrostatic stabilisation by a neighbouring ion or dipole, an effect which is enhanced in an environment of low dielectric constant. Hydrolysis of 2-(2'-carboxy-phenyl)-4,4,5,5-tetramethy1-1,3-dioxolan shows an isotope effect larger than the corresponding dioxolan without the carboxyl group in agreement with some carbonium ion character in the transition state. This was rationalised by competition by the neighbouring carboxyl group with the displaced alcohol for the carbonium ion. A new synthesis of a deuterated aldehyde is described which might be general for aldehydes which will not form benzoins readily.
Notlar:
School code: 0547
Konu Başlığı:
Tüzel Kişi Ek Girişi:
Mevcut:*
Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684601.1) | 684601-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
On Order
Liste seç
Bunu varsayılan liste yap.
Öğeler başarıyla eklendi
Öğeler eklenirken hata oldu. Lütfen tekrar deneyiniz.
:
Select An Item
Data usage warning: You will receive one text message for each title you selected.
Standard text messaging rates apply.