Methoxy cation, decomposition

This diastereoselective decomposition can be rationalized by the steric hindrance in the cis products as the coordination of the CpFe(CO)2+ fragment is prohibited by the relative orientation of the substituents (Scheme 9.13). Consequently, the rate of decomposition is enhanced when the substituents stabilize cationic ring-opened intermediates, such as in the methoxy derivative 11 (0% yield). On the other hand, the rate of decomposition of the trans products is reduced, based on the destabilization of cationic intermediates when an electron-withdrawing substituent, such as in the nitro derivative 13, is used (78%, cis trans = 4 1). 

The population of surface defects and coordination vacancies drives alkoxide and carboxylate formation and decomposition. When cations have at least two coordination vacancies, bimolecular reactions are possible (e.g., acetone from acetate ions, dimethylether from methoxy groups). 

Treatment of A-nitroso-iV-(cr5-2-phenylcyclopropyl)urea with excess sodium formate in methanol at 25 "C for 15 hours affords ( )-3-methoxy-l-phenylprop-l-ene (25%) and 3-methoxy-3-phenylprop-l-ene (60%, Table 15, entry 7). An almost identical result is obtained when the tran -isomer is used as substrate. Formation of the 2-phenylcyclopropyldiazonium ion, decomposition with loss of nitrogen to the 2-phenylcyclopropyl cation, followed by ring opening to form the phenylallyl cation, can explain the result. When [l- Hi]aminocyclopropane is subjected to deamination with nitrous acid in water at 0°C (Table 15, entry 8), allyl alcohol is obtained, which is isolated as the 4-(phenylazo)benzoate derivative in 44% yield. In this case, the deuterium is only located at the C2 allyl position. ... 

If the /7-position of the amine is blocked by methoxy, methyl, chlorine or bromine groups, the species is stable with respect to dimerisation and higher anodic potentials are required for its further oxidation. However, further decomposition of the tri /7-anisylamine radical cation occurs in the presence of any traces of cyanide ion present in the acetonitrile solution. Primary aromatic amines, like phenols, tend to polymerise upon oxidation unless the o and p positions are blocked. 2,4,6-tri-t-butylaniline in acetonitrile solution yields a fairly stable radical cation which in the presence of water forms 3,5-di-f-butyl-4-amino-2,5-cyclohexadienone. ° ... 

The adsorption of molecular probes, followed by infrared or NMR spectroscopy and thermal desorption studies, is the most commonly adopted way to study basic sites. Carbon dioxide is frequently used in infrared studies, particularly of cationic zeolites with added alkali metals.Chloroform is also suitable, since the interaction with the chlorine atom and subsequently the C-Cl stretching frequency is a measure of the basic strength. NMR studies of basic zeolites have concentrated on the use of C containing probes such as methyl iodide and chloroform. Addition of methyl iodide results in its decomposition and the formation of methoxy groups at framework oxygens. The shift of the methyl carbon is expected to be related to the basicity of the framework, that is the tendency of the framework oxygens to donate electrons - C MAS NMR of methoxy groups prepared in this way shows a clear distinction between basic zeolites, such as Cs-X, and acidic zeolites, such as H-ZSM-5. 

---