2-(2-mandelyl)thiamin (MTh), the adduct of benzoylformate and thiamin, is an accurate model of 2-(2-mandelyl)thiamin diphosphate, the initial covalent intermediate in the decarboxylation of benzoylformate by benzoylformate decarboxylase (BFDC). The first order rate constant for spontaneous decarboxylation of MTh is about 106 times smaller than the enzymic rate (kcat) for the BFDC reaction. Based on the similarities of MTh and the corresponding enzymic intermediate, as well as the inherent nature of the intermediate, it is not obvious why the enzyme-catalyzed reaction is so much faster. However, earlier studies showed that the decarboxylation of MTh is catalyzed by protonated pyridines and this was proposed to occur through a preassociation mechanism. If this explanation is correct, then the observed 12C/13C kinetic isotope effect (CKIE) will increase in the presence of the catalyst as a more favorable forward commitment is made possible. This provides a specific model for the enzyme-catalyzed process. We developed a technique using headspace analysis and compound specific isotope analysis (CSIA) to determine the CKIE for the decarboxylation of MTh in the presence and absence of pyridinium. We found that the CKIE increases in the presence of the catalyst, as predicted for the preassociation mechanism. In a related study, we investigated the kinetics of decarboxylation of pyrrole-2-carboxylic acid, which was known to be subject to acid catalysis in highly acidic solutions. In the expected mechanism, protonation of the pyrrole ring at C2 destroys the aromaticity of the ring. C-C bond cleavage in the process of decarboxylation will re-establish the aromatic pyrrole. However, the overall reaction rate would not increase as it is counteracted by a larger concentration of the undissociated carboxyl group compared to carboxylate ion necessary for decarboxylation. Since the reaction occurs readily, there must be an alternative pathway for the acid-catalyzed reaction. This can be achieved in an associative mechanism that is initiated by addition of water to the carboxyl group of the carboxyl-protonated reactant. C-C bond cleavage results in formation of pyrrole and protonated carbonic acid, a species that has been recognized as a viable intermediate in related processes. Protonated carbonic acid is spontaneously converted to H3O+ and carbon dioxide. The associative mechanism is consistent with solvent-deuterium kinetic isotope effects and 12C/13C kinetic isotope effects.

2-(2-mandelyl)thiamin (MTh), the adduct of benzoylformate and thiamin, is an accurate model of 2-(2-mandelyl)thiamin diphosphate, the initial covalent intermediate in the decarboxylation of benzoylformate by benzoylformate decarboxylase (BFDC). The first order rate constant for spontaneous decarboxylation of MTh is about 106 times smaller than the enzymic rate (kcat) for the BFDC reaction. Based on the similarities of MTh and the corresponding enzymic intermediate, as well as the inherent nature of the intermediate, it is not obvious why the enzyme-catalyzed reaction is so much faster. However, earlier studies showed that the decarboxylation of MTh is catalyzed by protonated pyridines and this was proposed to occur through a preassociation mechanism. If this explanation is correct, then the observed 12C/13C kinetic isotope effect (CKIE) will increase in the presence of the catalyst as a more favorable forward commitment is made possible. This provides a specific model for the enzyme-catalyzed process. We developed a technique using headspace analysis and compound specific isotope analysis (CSIA) to determine the CKIE for the decarboxylation of MTh in the presence and absence of pyridinium. We found that the CKIE increases in the presence of the catalyst, as predicted for the preassociation mechanism. In a related study, we investigated the kinetics of decarboxylation of pyrrole-2-carboxylic acid, which was known to be subject to acid catalysis in highly acidic solutions. In the expected mechanism, protonation of the pyrrole ring at C2 destroys the aromaticity of the ring. C-C bond cleavage in the process of decarboxylation will re-establish the aromatic pyrrole. However, the overall reaction rate would not increase as it is counteracted by a larger concentration of the undissociated carboxyl group compared to carboxylate ion necessary for decarboxylation. Since the reaction occurs readily, there must be an alternative pathway for the acid-catalyzed reaction. This can be achieved in an associative mechanism that is initiated by addition of water to the carboxyl group of the carboxyl-protonated reactant. C-C bond cleavage results in formation of pyrrole and protonated carbonic acid, a species that has been recognized as a viable intermediate in related processes. Protonated carbonic acid is spontaneously converted to H3O+ and carbon dioxide. The associative mechanism is consistent with solvent-deuterium kinetic isotope effects and 12C/13C kinetic isotope effects.

Course: Degree project in logistics, the Business Administration and Economics Programme Authors: Anna Jarenfors and Sissela Järsö Supervisor: Hana Hulthén Examiner: Helena Forslund Title: IPREP: Framework for elimination of an internal return process – A case study at Thule Sweden AB Background: Logistics coordination plays an important role regarding the competitive success of an organization. A company has to eliminate unnecessary processes involved in the supply chain in order to decrease cost and to improve the business. This study focuses on the problems with the internal return process at Thule Sweden AB. Thule Sweden AB has in the last decade had an increased production which have had led to a larger material flow which have impacted the internal return process negatively. The internal return process is, in this study, defined as the process where unused material in production is sent back to the warehouse. Purpose: The purposes of this study is to present suggestions of how the internal return process at Thule can be eliminated and construct a framework of how manufacturing companies can eliminate unnecessary internal return processes. Methodology: The study is a qualitative case study with an abductive approach of the internal return process at Thule Sweden AB. The theories used in the study are found from literature and scientific articles while empirical data has been collected mainly through semi-structured interviews and observations. The selection of interviewees has been based on what knowledge they carry and what responsibility they have in the company. Findings: A process map over the internal return process illustrated three general causes creating an internal return. These were incorrect material delivered to production, incorrect stock balance and leftover material after production. The three general causes found formed the basis of a fishbone diagram which identified seven root causes. The seven root causes presented were, not able to scan the barcode on the pallets, pallet put at incorrect production line, incorrect previous internal return, lack of stock counting at internal return, insufficiency in the material- and production planning, suppliers not able to produce in batch size and no kitting station. Suggestions of how to eliminate an internal return process were presented and the fundamental categories of the framework presented were integration, personnel, routines, environment and planning.   Key words: Internal return process, process elimination, general cause, root cause, framework, manufacturing company / Kurs: Examensarbete i logistik för Civilekonomprogrammet Författare: Anna Jarenfors and Sissela Järsö Handledare: Hana Hulthén Examinator: Helena Forslund Titel: IPREP: Framework for elimination of an internal return process – A case study at Thule Sweden AB Bakgrund: Logistikkoordinering spelar en viktig roll för ett företags konkurrenskraft. Ett företag måste eliminera onödiga processer i en försörjningskedja för att minska kostnader och förbättra verksamheten. Denna studie fokuserar på den interna returprocessen på Thule Sweden AB. Thule Sweden AB har under det senaste decenniet haft en ökad produktion vilket lett till ett större materialflöde som påverkat den interna returprocessen negativt. Den interna returprocesses är i denna studie definierad som den process där oanvänt material i produktion returneras till lagret. Syfte: Syftet med studien är att presentera förslag till hur den interna returprocessen kan elimineras samt att presentera ett ramverk över hur tillverkande företag kan eliminera onödiga interna returprocesser. Metod: Studien är en kvalitativ fallstudie, med ett abduktivt synsätt, över den interna returprocessen på Thule Sweden AB Teorierna använda i studien utgår från litterära källor samt vetenskapliga artiklar medan empirisk data samlats in mestadels från semi-strukturerade intervjuer och observationer. Urvalet av intervjurespondenter har baserats på vilket kunskap de erhåller samt vilka ansvarsområden de har i företaget. Resultat: En processkarta över den interna returprocessen illustrerade tre generella orsaker till det processen. Dessa var fel material levererat till produktion, felaktigt lagersaldo och överblivet material efter produktion. De tre generella orsakerna utgjorde grunden till ett fiskbensdiagram vilket identifierade sju rotorsaker till den interna returprocessen. De sju rotorsakerna var: omöjlighet att skanna streckkoden på pallen, pall transporterad till fel produktionslinje, felaktig tidigare intern returprocess, brist på inventeringsrutiner vid intern returprocess, ineffektivitet i material- och produktionsplaneringen, att leverantörer inte kan producera i batch-storlek samt brist på kittingstation. Förslag på hur den interna returprocessen kan elimineras presenterade och grundstenarna i det ramverk som presenterade var integration, personal, rutiner, omgivning och planering. Nyckelord: Intern returprocess, processeliminering, generell orsak, rotorsak, ramverk, tillverkande företag