Guanidines resonance stabilization

The even greater basicity of guanidine (p/iLa = 13-6) as compared with amidines is due to an even greater resonance stabilization of the cation, since three equivalent resonance structures enter into resonance [6]. The base itself resonates between three nonequivalent structures [37], and has according to Pauling (1939,... 

Resonance stabilization of the conjugate acid of guanidine defines this class of molecules as some of the strongest bases in organocatalysis [114],... 

Protonation of guanidine gives an ion that is stabilized by four resonance forms, three of which are equivalent. This gives a large amount of resonance stabilization to the protonated form, making guanidine easily protonated and thus a good base. 

The exceptional basicity of phosphazenes (iminophosphoranes) has been discovered by Schwesinger [83]. The phosphazene derivatives have been proved to be chemically very stable, kinetically active and highly versatile, and the large number of these bases has been synthesized. The gas phase and solution equilibrium basicity measurements for a large number of phosphazenes are conducted by Kaljurand et al. [84], and their PA and pAia values are published in various papers. These measurements show that phosphazenes surpass in their basicity the derivatives of acychc or bicyclic guanidines, amidines and vinamidines (Table 2.11). Extraordinary basicity of phosphazenes was theoretically rationalized by Maksic et al. [85], in terms of effective resonance stabilization of protonated molecules [86]. 

Guanidine itself is an extremely strong base because its protonated form is resonance stabilized ... 

Guanidine is a strong neutral base because its conjugate acid is resonance stabilized. (10.4)... 

The reaction between the above carbodiimides and the sodium caprolactamate takes place in part in the liquid system, producing a resonance-stabilized guanidine anion (Scheme 27). In the initiation of the polymerization, the guanidine anion rearts with the lactam monomer by a proton exchange reaction... 

Guanidine is found in turnip juice, mushrooms, com germ, rice hulls, mussels, and earthworms. Its basicity is due to the formation of a highly resonance-stabilized conjugate acid. Draw its resonance forms. (Hint Review Section 20-1.)... 

The guanidine-type resonance, which is present in aliphatic guanidines, is stronger than that in the corresponding amidines, at least in the case of the cationic forms. 2-Aminopteridine and 2-aminoquinazoline cations are two examples of compounds in which hydration is stabilized by the presence of a guanidino group (32). 

Since the reactauit is stabilized by resonance, there must be some factor which further stabilizes the product. Also, the question arises whether the imine function or the amino group will receive the protons. We can account for guanidine s significant basicity and the fact that the imine group is protonated by considering the following resonance structures ... 

Of two possible structures A and B for the conjugate acid of guanidine, the more stable is the one that is better stabilized by electron delocalization. Which one is it Write resonance structures showing this electron delocalization. 

The guanidines and biguanides exhibiting antimicrobial activity derive from guanidine and guanylguanidine = biguanide respectively. These are alkaline substances, stabilized by resonance they form salts with acids. 

Guanidine and guanylguanidine (biguanide) are bases which are stabilized by resonance. They exhibit strong alkaline reaction in aqueous media and form salts with acids. Alkyl derivatives dispose of distinctive antimicrobial efficacy. 

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