Leaving groups table

The rate of hydrolysis in monocyclic /1-lactams can also be predicted from the basicity of the amino leaving group Table 5.4,H) [90]. 

Figure 13.6. Activation of carboxylates by uronium salts [5,10,17,18,84,96], X leaving group. Table 13.6. Preparation of amides using uronium salts as coupling agents.

Figure 14.2. Strategies for the preparation of ureas on solid phase. X leaving group. Table 14.4. Preparation of ureas from support-bound amines.

Increased angle strain at silicon always leads to a significant change of the stereochemistry toward retention for exocyclic leaving groups (Table XVII). This general trend is particularly increased with the most angle-... 

But that is not our only option. The reactivity and hence the structure of the carbon electrophile matter too. If we want reaction at a methyl group we can t change the carbon skeleton, but we can change the leaving group. Table 17.4 shows what happens if we use the various methyl halides in reaction with NaOH. 

In the case of good anionic leaving groups, such as phosphate cf. [38], sulfate [39], or halogen [40], these can be eliminated directly by bond heterolysis. These eliminations can be very fast even in the absence of base catalysis, the rate depending on the state of protonation of the leaving group (Table 2). 

Two series of compotmds were prepared in order to distinguish the electrochemical behavior of o - and o -complexes. The first one, o -complexes (H as nucleophile) of nitroaromatic compounds with a different number of nitro groups in the ring (Table 1) [22]. The second one, o - and o -complexes of nitroaromatic compounds with diverse leaving groups (Table 2) [23]. 

The problem is that OH is an extraordinarily poor leaving group (Table 7.4). The of water is 15.7. Water is a rather weak acid, and its conjugate base, hydroxide... 

Another technique for changing the leaving group uses a two-step process in which the alcohol is first converted into a sulfonate. Sulfonates are excellent leaving groups (Table 7.4) and can be displaced by all manner of nucleophiles to give desirable products (Fig. 7.41). 

Other well-known G-nerve agents contain fluor (i.e., sarin, soman, and cyclosarin), whereas tabun contains —CN as a leaving group (Table 57.2, Figure 57.3). However, sarin and soman have one substitution by a P—O—bond, and another has a P=C bond, so they are usually named phosphonates. Phosphoroamidate compoimds have also been synthesized with a non-substituted amido group (P-NH2/ i e., methamidophos)... 

Upon ionization, chloride ion does not immediately diffuse away from the intermediate allylic cation. Reattachment to give either starting material or its allylic isomer occurs—recall the reversibility of S>jl reactions (Exercise 7-3). However, chloride continues to dissociate, allowing acetate, a good nucleophile but a poor leaving group (Table 6-4), to win out ultimately. 

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