Reaction predicting products

Acyl isocyanates (13,X = O, S) have been shown to react as heterodienes ia most cycloadduct formations. Notable examples iaclude autodimerization and the addition to imines (46,47). Unlike aromatic isocyanates, it is not possible to predict the reaction pathway nor the stmcture of the products which may arise from a given approach or set of reaction conditions. 

Interactive to practice predicting products of addition reactions according to Markovnikov s rule... 

Thomson wVY Click Organic Interactive to use a web-based palette to predict products for alkyne addition reactions. 

Interactive to learn to predict products in Michael-style addition reactions. 

Thomson I Click Organic Interactive to predict products from reactions of simple monosaccharides. 

ThomsonNGW Click Organic Interactive for an interactive exercise in predicting products from cycloaddition reactions. 

Le Chatelier s Principle, the removal of Zn+2 tends to shift equilibrium toward the products. Therefore, removing Zn+2 increases the tendency for reaction (63) to occur. Our prediction of reaction is still valid. 

A gas chromatographic analysis of the reaction products showed that although some of the predicted side reactions do occur, their magnitude would not be sufficient to account for the large deviations of the Hammett plots. 

The predicted product shown in Fig. 1.14 is different from that shown in Fig. 1.13, even though the reactants are the same. Of course it is nonsense to think that the product of a reaction between two species could depend upon the relative positions of their formulas in a representation of a reaction equation This is clear evidence that some students consider the juxtaposition of the written representations of the reactants on the page, rather than a visualisation of the reaction mixture at the sub-microscopic level. The quality of the predictions would have been greatly enhanced if the students had visualised a many-particle, probabilistic picture of the reaction mixture, as discussed earlier... 

Until now, we have learned the basic terminology that you will need in order to predict products of addition reactions. To summarize, there are three pieces of information that you must have in order to predict products ... 

Synthesis is really just the flipside of predicting products. In any reaction, there are three groups of chemicals involved the starting material, the reagents, and the products ... 

For ketones and aldehydes in which adjacent substituents permit the possibility of chelation with a metal ion, the stereochemistry can often be interpreted in terms of the steric requirements of the chelated TS. In the case of a-alkoxyketones, for example, an assumption that both the alkoxy and carbonyl oxygens are coordinated with the metal ion and that addition occurs from the less hindered face of this chelate correctly predicts the stereochemistry of addition. The predicted product dominates by as much as 100 1 for several Grignard reagents.120 Further supporting the importance of chelation is the correlation between rate and stereoselectivity. Groups that facilitate chelation cause an increase in both rate and stereoselectivity.121 This indicates that chelation not only favors a specific TS geometry, but also lowers the reaction barrier by favoring metal ion complexation. 

Experimental probes of Born-Oppenheimer breakdown under conditions where large amplitude vibrational motion can occur are now becoming available. One approach to this problem is to compare theoretical predictions and experimental observations for reactive properties that are sensitive to the Born-Oppenheimer potential energy surface. Particularly useful for this endeavor are recombinative desorption and Eley-Rideal reactions. In both cases, gas-phase reaction products may be probed by modern state-specific detection methods, providing detailed characterization of the product reaction dynamics. Theoretical predictions based on Born-Oppenheimer potential energy surfaces should be capable of reproducing experiment. Observed deviations between experiment and theory may be attributed to Born-Oppenheimer breakdown. 

The PMO calculation for the benzaldehyde-trimethylene reaction is given in Table 4.12 and that for acetone and dicyanoethylene in Table 4.13. The predicted products based on the PMO calculations for these two reactions agree very well with the experimental results given in the previous sections. 

While this scheme is useful in helping to predict products from di-rr-methane rearrangements, all evidence indicates that the structures drawn are not intermediates in the reaction. That is, they do not represent energy minima on the potential energy surface leading from the excited state of the reactant to the ground state of the product. 

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