Alkoxyl groups

For the Birch reduction of mono-substituted aromatic substrates the substituents generally influence the course of the reduction process. Electron-donating substituents (e.g. alkyl or alkoxyl groups) lead to products with the substituent located at a double bond carbon center. The reduction of methoxybenzene (anisole) 7 yields 1-methoxycyclohexa-1,4-diene 8 ... 

Several determinations of the number of propagation centers by the quenching technique have been carried out (98, 111). As a quenching agent methanol, labeled C14 in the alkoxyl group, proved to be suitable in this case. The number of active centers determined by this technique at relatively low polymerization rates (up to 5 X 102 g C2H4/mmole Cr hr at 75° and about 16 kg/cm2) (98, 111, 168) in catalysts on silica was about... 

Carbon-14 of the alkoxyl group in the polymer was also found during the treatment by other oxide polymerization catalysts containing the oxides Mo, W, V (195). By the character of the polarization of the active bond such systems may be designated coordinated cationic. ... 

The alkoxyl group OR is not a leaving group, so these compounds must be converted to the conjugate acids before they can be hydrolyzed. Although 100% sulfuric acid and other concentrated strong acids readily cleave simple ethers, the only acids used preparatively for this purpose are HBr and HI (10-71). However, acetals, ketals, and ortho esters are easily cleaved by dilute acids. These compounds are... 

The situation with 7V-acyloxy-/V-alkoxyureas and carbamates is similar although infrared data were mostly determined by liquid film or condensed phase (KBr/nujol mull).52,131 However, the limited data for V-acyloxy-TV-alkoxyureas (Table 2, entries 69-72) give amide carbonyl frequencies ca. 1730 cm-1 that are raised by some 37-40 cm-1 by acyloxylation. Values for carbamates (Table 2, entries 73-77) are higher (mostly 1780 cm-1) but are raised to a lesser extent (10-20 cm-1) relative to their parent carbamates. Clearly, carbonyl vibrational frequencies will be influenced strongly by the adjacent amino or alkoxyl group in both analogues. 

These rearrangement processes are characterised by a transition state in which the alkoxyl group migrates from the amide nitrogen to the carbonyl carbon (Fig. 17a) and therefore involves HEteroatom Rearrangements On Nitrogen the HERON... 

The physical and spectroscopic properties of /V-acyloxy-A-alkoxyamides confirm pyramidality at nitrogen and the disconnection of the nitrogen lone pair from the amide carbonyl. The presence of an acyloxyl and an alkoxyl group at nitrogen also results in an anomeric interaction between the oxygens, which is facilitated by the sp3-hybridised nitrogen. Experimental observations, including X-ray analysis are fully supported by results from computational chemistry. 

Fig. 39.—,3C-N.m.r. Spectra of A, 0-(Carboxymethyl)cellulose (d.s. 0.7), Partially Degraded by Cellulase, in D20 at 30° (R, signal of reducing-end residue S represents a 13C nucleus bonded to an alkoxyl group) and of B, 0-(2-Hydroxyethyl)cellulose (d.s. 0.8), Partly Degraded by Cellulase, in D20 at 30°. (R, signal due to reducing-end residue S represents a 13C nucleus bonded to an alkoxyl group.)...

Since, in this method, six equivalents of iodine are liberated for each alkoxyl group, the determination can be made with great accuracy even when the amounts of substance are very small. 

Large changes in nitrogen hyperfine interaction are brought about by attachment either of alkoxyl groups or of acyl groups to the nitroxide nitrogen. In an alkoxy alkyl nitroxide, aN rises to nearly 30 G, whilst a typical acyl alkyl nitroxide has an aN-value of ca. 8 G, and in diacyl nitroxides this may fall below 5 G (Lemaire and Rassat, 1964). 

Based on NMR evidence as well as analogy with results obtained with isoquinolinium salts, it appears certain that adducts (6) obtained from vinyl ethers invariably have the alkoxyl group turned away from the quaternary nitrogen or, in other words, are syn with respect to the... 

This chapter will cover the synthesis, structure and chemical reactivity of various N-heteroatom-substituted hydroxamic esters, anomeric amides in which at least one of the heteroatom substituents at nitrogen is an alkoxyl group. Throughout this review, these will either be referred to as A-substituted hydroxamic esters or as A-substituted-A-alkoxy amides. 

Alkoxyl and acetoxyl protons in A-acetoxy-A-alkoxybenzamides give rise to sharp signals well below room temperature. In contrast, hydroxamic esters usually exhibit line broadened alkoxyl group resonances in their H NMR spectra at or even signihcantly above room temperature" . In toluene-rfg, the benzylic and acetoxyl methyl resonances of A-acetoxy-A-benzyloxybenzamide (100) showed signihcant line broadening below 250 K but remained isochronous down to 190 K. 

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