Introducing the Reagent

Samarium(II) iodide (Sml2) is commercially available as a solution in THF or can be prepared readily using one of several straightforward methods that have 

Organic Synthesis Using Samarium Diiodide A Practical Guide By David J. Procter, Robert A. Flowers, II and Troels Skrydstrup David J. Procter, Robert A. Flowers, II, Troels Skrydstrup 2010 Published by the Royal Society of Chemistry, www.rsc.org 

Lanthanides Chemistry and Use in Organic Synthesis-, S. Kobayashi, Ed. Springer, 1999, 155. Dahlen, G. Hilmersson, Eur.J. Inorg. Chem., 2004, 3393. 

Polymer chemistry - Agarwal, S. Greiner, A. J. Chem. Soc., Perkin Trans. 1, 2002, 2033. 

The chemistry of samarium enolates- Rudkin, I. M. Miller,L. C. Procter, D. J., Organomet Chem., 2008, 34,19. 

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The order of introducing the reagents may also affect the composition of the nitration product. For example, if the toluene is added to the acid, then the first portions of toluene come into contact with a large excess of acid, and the nitration process may proceed beyond mononitration resulting in a mixture of di- and mono-nitrotoluene. If the amount of HN03 used has been calculated accurately, the last portions of toluene may be left unnitrated and the resultant product may not be uniform. If, on the contrary, the acid is added to the toluene, an excess of acid cannot occur, since each portion added reacts with the toluene very quickly. 

Chemical Reactions Chemical reactions are influenced by the uniformity of concentration both at the feed point and in the rest of the tank and can be markedly affected by the change in overall blend time and circulation time as well as the micro-scale environment. It is possible to keep the ratio between the power per unit volume at the impeller and in the rest of the tank relatively similar on scale-up, but many details need to be considered when talking about the reaction conditions, particular where they involve selectivity. This means that reactions can take different paths depending upon chemistry and fluid mechanics, which is a major consideration in what should be examined. The method of introducing the reagent stream can be projected in several different ways depending upon the geometiy of the impeller and feed system. 

Kuhn and Wintcrslcin introduced the reagent for the conversion of 1,2-glycols into oleflns. Thus hydroclnnamoln is reduced in high yield to 1,6-diphenylhexatricnc. A suspension of the diol in ether is shaken with the reagent until conversion to the... 

The amount of boron trifluoride etherate 3 The amount of amine subtrate (benzylamine) 4 The order of introducing the reagents 5 Presence or absence of a drying agent... 

However, sometimes the order of introducing the reagents is not at all evident. Many established procedures belonging to this category smack of "witchcraft chemistry", where some innovator presented a procedure which is then followed by practioners in the field. 

Experiments which yield poor results by the above principles may still help to elucidate the reaction mechanisms. They represent introduction orders which involve a limiting factor For instance, a critical intermediate is not formed rapidly enough an intermediate is formed which undergoes a side reaction a higher-order complex between three or more constituents is necessary and the formation of such complexes is dependent on the order of introducing the reagents. 

Determination of Histidyl Groups. Horinishi et al. (20) introduced the reagent diazonium-l-H-tetrazole (DHT) for spectrophotometric determination of histidyl residues in proteins. The method has later been modified by Sokolovsky and Vallee (45). When the P. notatum cellulase (37) reacted with DHT a complete loss of activity was observed at a very low excess of reagent. The DHT is, however, a rather unspecific reagent and it is difficult to draw any definite conclusions about the reasons for the inhibition. 

The principle behind the FIA technique (reversed mode) has been exploited to develop a completely automated instrument [44] (Fig. 15.15) in which the sample is continuously pumped along the system and in which different injection valves [45] or a single injection valve aided by a selecting valve [46] are used to introduce the reagents required for the determination of each analyte in the appropriate sequence and at the required time intervals. The reacting plug is driven to the fiow-ceii of a photometric detector, and the... 

A chemiluminescence method has been described for the determination of PG in edible oils using the enhancing effect of this antioxidant on the luminescent signal of 2-phenyl-4,5-di(2-furyl)-lH-imidazole (PDFI) and potassium ferricyanide system in an alkaline medium [57]. The method involves the use of solid-phase extraction with a Cjg cartridge as the stationary phase for sample treatment. The interferents were retained on the cartridge while PG was eluted. A flow system was used to introduce the reagents (PDFI, sodium hydroxide, and potassium ferricyanide) and the sample into the sample cell of the instrument and to measure the enhanced chemiluminescence signal, which was linearly related to the PG concentration. A detection limit of 36 ng/mL PG was obtained. 

Miscellaneous Reactions. Bromodimethylborane can also be used to convert dialkyl, aryl alkyl, and diaryl sulfoxides to the corresponding sulfides (eq 15). Typically, the sulfoxides are treated with 2.5 equiv of Me2BBr in dichloromethane at —23 °C for 30 min and at 0°C for 10 min. Bromine is produced in the reaction and must be removed in order to avoid possible side reactions. This is accomplished by saturating the solution with propene prior to introducing the reagent or by adding cyclohexene. Phosphine oxides and sulfones failed to react under the conditions used to deoxygenate sulfoxides. 

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