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A general survey of the chemistry of oxaziridines is presented, previous studies on the mechanism of the acid and base catalysed hydrolysis are critically reviewed and the results discussed in relation with the hydrolysis of compounds with related structures. Results of the acid hydrolysis of several oxaziridines are reported and agree with previous findings. These accord with a mechanism involving the breakdown of an 0-conjugate acid intermediate to give either a carbonium ion or an immonium ion structure, which subsequently reacts-with water. The importance of each pathway depends on the nature of the 3-substituent. The proton α to the ring nitrogen seems to be involved in the rate determining step for the reaction of 2-primary-alkyl 3-alkyl oxaziridines. For 2-secondary-alkyl 3- alkyl compounds extensive migration of an α group occurs and steric requirements and migratory aptitudes seem to be important. Investigations of the site of protonation suggest N as the most likely site, although hydrolysis probably proceeds via the 0-conjugate acid: pKA values for oxaziridines reflect the nature of the 3-substituent as well as the degree of branching at position 2 and lie in the range -1.9 to +0.30. Results of basic hydrolysis of several oxaziridines are reported and are consistent with earlier findings. The hydrolytic mechanism 'which rationalisesall the data is a heterolytic bimolecular rate determining abstraction of an 0( proton to the ring nitrogen by the base.

Concerns about student retention and attrition rates in higher education have been steadily increasing over the years. Efforts to identify and treat potential withdrawers have grown considerably; now, more than ever, universities are getting more competitive and financially driven, as the issue of student attrition is threatening to affect the way in which universities continue to run (Harvey, Drew & Smith, 2006). More universities are now developing strategic retention plans that aim at keeping students enrolled in their courses, as there is no doubt that as attrition rates increase, universities’ funding could be at risk (Schwartz, 2007). Literature on student attrition and retention in higher education shows that there has been a substantial amount of research conducted into the issues of attrition and retention in general. Varied conceptual models have been developed to explain and acknowledge student attrition as problematic and these models have focused on determining the factors contributing to student withdrawal, as well as the elements that contribute to student success. However, until now, the literature available shows that there seems to be a shortage of research into the area of foreign language student attrition and retention. As the number of students learning a foreign language in Australian high schools is at its lowest ever, this lack of research is worrying (Group of Eight, 2007). This ultimately illustrates the importance and significance of research studies conducted to determine the reasons why students are withdrawing from foreign language classes at tertiary institutions. This study investigates student attrition and develops a prognostic approach to identify students at risk of withdrawing from their courses. The study was divided into three stages. The first stage examined class assessment reports to provide a picture of existing attrition rates in the course being examined, Elementary Spanish. The second stage explored factors contributing to withdrawal, using survey and interview data collected from 12 students who withdrew from Elementary Spanish, identifying probable factors triggering withdrawal, and comparing these factors to those identified in the literature. These data were contrasted with those collected from 24 students who did not withdraw. The third stage saw the development and piloting of a prognostic instrument and approach aimed at identifying students potentially at risk of withdrawal, using theoretical insights gained from the previous two stages. Previous studies have taken a diagnostic approach to attrition—that is, looking at the problem after it has taken place. The prognostic instrument was piloted with a group of 18 first year Elementary Spanish students in 2007 to identify those at risk of withdrawal, and to evaluate the performance of the instrument. As a result of the pilot in 2007 parts of the approach were improved and in 2008 it was implemented on a group of 31 students. The results were positive in determining which students could be at risk. While the study examined Spanish language students, and thus the results may not be applicable to other languages or other disciplines, this study was the first of its kind in taking a prognostic rather than diagnostic approach to an issue of great importance to both education providers and students.