Sökning: "substitution"

Visar resultat 6 - 10 av 752 avhandlingar innehållade ordet substitution.

1. 6. Concerted or Stepwise? : β-Elimination, Nucleophilic Substitution, Copper Catalysed Aziridination and Ruthenium Catalysed Transfer Hydrogenation Studied by Kinetic Isotope Effects and Linear Free-Energy Relationships

   Författare :Per Ryberg; Heinz F. Koch; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Organic chemistry; Kinetic isotope effect; linear free energy relationship; elimination; substitution; aziridination; transfer hydrogenation; Organisk kemi; Organic chemistry; Organisk kemi; organisk kemi; Organic Chemistry;

   Sammanfattning : This thesis describes the use of kinetic isotope effects, linear free energy relationships and stereochamical studies to distinguish between different mechanistic alternatives and to obtain information about transition state structure.In the first part fluorine and deuterium kinetic isotope effects were determined for the base promoted HF elimination from 4-fluoro-4-(4’-nitrophenyl)butane-2-on. LÄS MER

3. 7. Direct Catalytic Nucleophilic Substitution of Non-Derivatized Alcohols

   Författare :Anon Bunrit; Joseph Samec; Joseph Moran; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; nucleophilic substitution; catalysis; alcohols; stereospecific; Lewis acid; Brønsted acid base; bifunctional; heterocycles; organisk kemi; Organic Chemistry;

   Sammanfattning : This thesis focuses on the development of methods for the activation of the hydroxyl group in non-derivatized alcohols in substitution reactions. The thesis is divided into two parts, describing three different catalytic systems. LÄS MER

4. 8. Copper-Mediated Vicarious Nucleophilic Substitution

   Författare :Olof Haglund; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : This thesis suggests and examines a novel approach for copper-mediated cross-couplings. We call this mechanistic approach copper-mediated vicarious nucleophilic substitution. Our hypothesis is that copper-promoted cross-couplings proceed via an intermediate s-adduct, a Meisenheimer adduct. LÄS MER

5. 9. Chemicals in consumer products : Towards a safe and sustainable use

   Författare :Linda Molander; Christina Rudén; Sven Ove Hansson; Mattias Öberg; KTH; []
   Nyckelord :consumer products; articles; hazardous chemicals; risk management; chemicals regulation; REACH; substitution; regulatory toxicology; European Union;

   Sammanfattning : Health and environmental risks associated with emissions of hazardous chemicals from articles, including everyday consumer products such as clothes and toys, have become widely acknowledged internationally, particularly in the EU. This thesis contributes to new understandings of how these risks are currently managed within the EU and recommends actions for ensuring a safe and sustainable use of chemicals in articles. LÄS MER

7. 10. Welfare Relationships : Voluntary organisations and local authorities supporting relatives of older people in Sweden

   Författare :Lena Dahlberg; Rune Premfors; Tommy Möller; Staffan Johansson; Stockholms universitet; []
   Nyckelord :SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; substitution; complementarity; welfare pluralism; voluntary organisation; welfare state; informal care; older people; Sweden; Political science; Statsvetenskap;

   Sammanfattning : Sweden is often described as a country with a strong welfare state and little voluntary work. This is as would be expected according to substitution theory, in which extensive welfare systems are assumed to crowd out voluntary activity and thereby limit the potential for voluntary work – there is an inverse relationship between voluntary and statutory activity. LÄS MER