Depending on the structure of the organic contaminant, different reactions may occur such as the addition of some substance attracted by electrons, such as a cathion or a molecule whose atoms have electron deficiency, and tend to link by covalent link to a nucleophile
, causing a electrophilic reaction with substances containing unsaturations and aromatic rings, electronic transference and radical-radical reactions (AGUIAR et.al., 2007).
It was logical to assume that [alpha], [beta]-unsaturated ketone group in the each diterpenoids could undergo the nucleophilic addition with nucleophile
compounds such as L-cysteine in DMEM.
was performed using 7-methoxyindole (6) as a nucleophile
, two kinds of the expected indolic dimer (23, 24) were obtained (Fig.
However, the molecule is sterically hindered, making it a weak nucleophile
A virus (HAV) 3C peptidase was the first structure identified for a viral 3C enzyme that exhibited the three-dimensional fold of the chymotrypsin family of serine peptidases but had a cysteine sulfur atom instead of the serine oxygen as the nucleophile
. The structure of HAV 3C was unusual in that the Asp residue expected as the third member of the catalytic triad did not interact with the general base His (James, M.
In the model represented in Scheme 3, D, S and N refer to the detergent monomer, substrate and the nucleophile
, respectively, while DnS and DnSN refer to the binary and ternary complexes, respectively.
Evidence for the involvement of a E-cycloalkenone intermediate was obtained when irradiation was performed at low temperature, followed by addition of the nucleophile
in the absence of light, which afforded the addition product in ~ 20% yield.
Essentially every compound targeted and prepared is new because of the difficulty inherent in other methods, and the syntheses represent another group of reactions where an anionic nucleophile
is condensed with an anionic electrophile.
Inspection of Table 2 reveals the reactivities of the new molecules; molecule 4 is the most susceptible molecule to electrophilic attack due to its large N value of 1.21 eV and smaller w value of 2.49 eV, whereas molecule 3 is the most likely attacked by a nucleophile
. Molecule 3 is of highest chemical potential (=-4.77 eV), lowest nucleophilicity N (=0.60 eV), and of considerable high electrophilicity (=3.02).
compound and zinc oxide are mixed with the polymer base at the first mixing step.
Thus, similarly, a large deshielding of carbon 7 would be expect if the hydroxyl 1 had reacted, which was not observed, confirming that hydroxyl 3 was again the nucleophile
in the intramolecular reaction that gave (3'S,4'S)-1,6-dihydroxy-1',7',7',8-tetramethyl-2', 3', 4', 7' -tetrahydro-4H,9H-isochromene[2,3 -c]xanthen-9-one (6), with 7.5% yield.
Construction of the desired diacid monomer (Scheme 1) started with 1, 4-addition of oxygen nucleophile
 of to/-butyl acrylate to give (77%) the corresponding product 1, which was subsequently deprotected (formic acid) to afford (95%) diacid 2.