An improved preparation of a Grignard reagent

Eckert, Timothy S.

doi:10.1021/ed064p179

Cited by 9 publications

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“…We previously examined the reaction of commercial zinc powder 1 with fluorophore-tagged organoiodides 2 and 3 in THF in the presence and absence of lithium chloride. 8 Three mechanistic possibilities were considered for the role of lithium chloride in the formation of soluble organozinc reagents from alkyl iodides and zinc powder: (1) lithium chloride cleans oxides from the surface of the zinc powder 31 before coordination or reaction of the alkyl iodide (similar to the role of I 2 in activating magnesium metal in Grignard reagent formation 32 ); (2) lithium chloride solubilizes surface organozinc reagents after oxidative addition, thus producing the solution-phase reagent and exposing the zinc surface to another molecule of alkyl iodide; 3 (3) lithium chloride accelerates oxidative addition, as suggested previously through calculations. 33 Probes 2 and 3 were designed such that the green BODIPY fluorophore was sufficiently removed electronically and spatially from the reactive carbon−iodide bond so as to serve as a spectator in the reaction and to avoid potential quenching from the zinc surface and electronic or steric interference with the insertion reaction.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder

2017

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Employment of fluorophore-tagged alkyl and aryl iodides permitted detection of persistent surface intermediates during their direct insertion to commercially available zinc powder. The sensitivity of this subensemble microscopy technique enabled structure–reactivity studies in the formation of intermediates that are present in quantities sufficiently low as to have been undetected previously by traditional ensemble analytical techniques. These surface intermediates were transformed by lithium chloride, leading to the assignment of the mechanistic role of lithium chloride as changing the rate-determining step in the reaction by lowering the barrier for solubilization of these otherwise persistent surface organometallic intermediates. The temperature dependence/qualitative barrier of the direct insertion step was determined independently from the solubilization step and from the barrier for the overall reaction. Detection of these zinc surface intermediates at the single-molecule level, i.e., of individual surface organometallic species, has been achieved for the first time. Energy dispersive X-ray spectroscopy (EDS) measurements of the elemental composition of the surface of the zinc powder determined that lithium chloride does not clean the surface of the oxides; instead, pretreatment of the surface with TMSCl effects partial removal of surface oxides after the 2 h pretreatment time previously reported in the empirically optimized synthetic procedure. Current limitations of this microscopy approach are also determined and discussed with respect to the addition of solid reagents during in operando imaging. Characterization of the resulting soluble fluorophore-tagged organozinc/LiCl complex by 1H NMR spectroscopy, mass spectrometry, and fluorescence spectroscopy provided insight into its solution dynamics and chemical exchange processes.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder

2017

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“…To further explore the conversion of sulfinate 1a , a more reactive nucleophile such as a Grignard reagent was used for a faster reaction. The reaction of phenylmagnesium bromide with sulfinate 1a could be considered as a continuation of the preparation of a phenylmagnesium halide 6 , a common experiment performed in undergraduate organic chemistry laboratories . Additionally, sulfoxide 5a is an easily isolated product with desirable physical properties .…”

Section: Results and Discussionmentioning

confidence: 99%

The Two Faces of Sulfinates: Illustrating Umpolung Reactivity

et al. 2016

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A simple, microscale experiment was developed with the aim of demonstrating the concept of umpolung in synthetic organic chemistry. Starting from a common alkyl sulfinate, students perform a polarity inversion by performing a Grignard-based sulfoxide synthesis and a Mannich-type formamide synthesis. The products are purified without chromatography and are easily characterized. Procedural optimization established an experiment time of less than 3 h. Spectroscopic characterization includes the interpretation of 1H NMR, 13C NMR, and FTIR spectra. This experiment, therefore, is suitable for a mid- to upper-level undergraduate organic lab curricula for illustrating advanced synthetic methods.

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“…One time when they did respond well was when I tried Eckert's [3] idea for introducing the />-value in a hypothesis test. The class quite happily told me that the probability of obtaining a red card from a pack of cards was one half and that it would remain one half if the card was replaced and the pack shuffled.…”

Section: Interactionmentioning

confidence: 99%

Ideas for improving statistics education

Hollis

1997

International Journal of Mathematical Education in Science and

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This paper looks at ideas that have been tried in an effort to dispel some of the negative feelings that students bring with them to introductory statistics courses at university. Relevance, involvement, interaction, use of computers and videos were investigated and the students' responses monitored. Students enjoyed a break from a standard lecture/tutorial and responded well to participating in experiments, provided that the tutor was enthusiastic. Videos were also appreciated as an alternative mode of presentation, although to gain maximum benefit from videos they must be properly integrated into the course. In an assignment aimed primarily to promote relevance, one group of students found it difficult to see the relevance of statistics to their course as they had difficulty finding suitable data, but another group, who collected and analysed data on a topic of interest, became very interested in the analysis and results. Even though all ideas were inevitably not a complete success at the initial implementation there was ample positive feedback to appreciate the need to keep trying new ideas in order to stimulate interest in introductory statistics.

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An improved preparation of a Grignard reagent

Cited by 9 publications

References 0 publications

Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder

Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder

The Two Faces of Sulfinates: Illustrating Umpolung Reactivity

Ideas for improving statistics education

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