Tert-Amyl group

Table 15 shows that peroxyester stabiUty decreases for the alkyl groups in the following order tert — butyl > tert — amyl > tert — octyl > tert — cumyl > 3 — hydroxy — 1,1 dimethylbutyl. The order of activity of the R group in peroxyesters is also observed in other alkyl peroxides. Peroxyesters derived from benzoic acids and non-abranched carboxyUc acids are more stable than those derived from mono-a-branched acids which are more stable than those derived from di-a-branched acids (19,21,168). The size of the a-branch also is important, since steric acceleration of homolysis occurs with increasing branch size (236). Suitably substituted peroxyesters show rate enhancements because of anchimeric assistance (168,213,237). 

Figure 4.21 shows how the bulkiness of the base influences the regioselectivity of the elimination of HBr from tert-amyl bromide. The stericahy undemanding base EtO can react with the H atoms in all -positions to the leaving group, irrespective of whether the H atom is bound to a primary or a secondary C atom. Thus, regioselectivity derives from product development control alone the thermodynamically more stable Saytzeff product is formed preferentially, though not exclusively. 

Activities lower than those of pyrocatechol were found with all the observed substances of Type la, where R- = ferf-alkyl group (a) 1,1-dimethylethyl (denoted further as tert-butyl), (b) 1,1-dimethylpropyl (tert-amyl), (c) 1,1,3,3-tetramethylbutyl (tert-octyl), and (d) 1,1,3,3,5,5-hexamethylhexyl (tert-dodecy ) the relative activities (calculated from... 

All tertiary alkyl groups (a-d) are branched in the same way on the a-carbon atom and differ in the length of the carbon chain and the nature of further branching the activity first decreases until substitution by the alkyl group with three carbon atoms in the main chain (i.e., tert-amyl), then it increases to the ferf-dodecyl group (C6 chain) nevertheless, the... 

The alkyl-group substituent R on the anthraquinone differs from manufacturer to manufacturer. In addition to 2-ethyl- (mainly used), 2-tert-butyl-, 2-tert-amyl- and 2-sec-amyl-anthraquinones are also utilized. Mixtures of different alkyl anthraquinones can also be used. 

The ketone group in trialkyl phosphonoglyoxylates is highly electrophilic, being quantitatively converted to the hydrate by addition of one equivalent of water, and there is no evidence for rapid exchange on the NMR time scale. The hemi-acetal from methanol also forms quantitatively and showed no sign of conversion to hydrate when kept 48 h in water at room temperature. However, one equivalent of a more hindered tert-amyl) alcohol gave only about 5% hemiac-etal. 

For the other fuel oxygenates detailed studies on the reaction pathways are not as abundantly available in literature. However, the similarity in chemical structure implies similar reaction by-products. In the case of TAME, tert-amyl formate and tert-amyl alcohol were observed instead of fBF and fBA, and their subsequent degradation products however, acetone and methyl acetate were observed as well [117]. The attack on the methoxy group was observed to be the major pathway, corresponding to the MTBE ehmination. During the elimination of ETBE the same reaction by-products were observed as with MTBE, with the exception of fert-butyl acetate which was formed instead of fBF [30]. 

Since both reactions take place by nucleophilic substitution, the electronegativity and the size of alkoxy groups is important. By using a large branched alkoxy group (tert-amyl alkoxide), the reaction rate can be reduced, resulting in small-sized sols. An amorphous phase predominated in the xerogel... 

Reactions of this kind formally involve rearrangements of intermediate carbonium ions by a 1,2 migration of alkyl. In this case the carbonium ion initially formed is an unstable primary ion. The rearrangement leads to its conversion to a tertiary carbonium ion in which three — / alkyl groups are attached to the cationic center. The products are then derived from the resulting tert-amyl cation rather than neopentyl. 

Approximately 15% of the photolysed hydroperoxide groups are reported to undergo a )5-scission reaction [383]. Several low molecular peroxides such as tert-amyl hydroperoxide, di-tcrf-butyl peroxide, 1,1-dienonylethyl hydro-... 

A drastic change of nitroxide stmcture was witnessed with the use of the commercially available DBNO (27). In particular, Moad and Rizzardo showed that the dissociation rate constant of a DBNO-based alkoxyamine was higher than any similar alkoxyamines based on cyclic nitroxides bearing tetra-methyl alkyl groups on the vicinity of the aminoxyl function. The first experimental studies were performed by the group of Catala where it was shown that the polymerization of styrene and substituted styrene monomers could be carried out at 90 ° C with all the criteria of control/livingness. However, the polymerization rate was independent of the alkoxyamine concentration and remained governed by the production of thermal radicals in the medium. The tert-butyl-tert-amyl nitroxide 28 was tested by Moad et to control the polymerization of MMA and appeared to be inefficient. 

As detailed by Smith et al. (1995), tert-amyl formate is the major expected product from attack at the CH3 group adjacent to the ether linkage,... 

Langer and Ljungstrom (1994b) have shown that the NO3-initiated oxidation of TAME proceeds mainly via abstraction from the CH3O group, leading to the main product tert-amyl formate, observed in 80% yield. 

Potassium Alkoxides. The most widely used potassium bases are potassium tert-hu. oAde [865-47-4] (KTB) and potassium / i -amylate [41233-93-6] (KTA). These strong alkoxide bases offer such advantages as base strength (pX = 18), solubiUty (Table 5), regio/stereoselectivity because of bulky alkyl groups, and stabiUty because of the lack of a-protons. On storage, KTB and KTA have long shelf Hves under inert atmosphere (see... 

It was shown that amide formation can be suppressed by the appropriate choice of reaction conditions, such as homogeneous solutions, e.g. in DMF, DMSO, HMPA, high acidity and low temperatures (-30 to -5°C). If the peptide hydrazide contains acid-labile protecting groups, e.g. trityl, 2-(4-biphenyl)propyloxycarbonyl, tert-butyloxycarbonyl, tert-butyl esters and ethers, the temperature has to be kept below -20 °C. Generally, tert-butyl or butyl nitrite is used as the organic nitrite, and for sterically hindered peptides amyl nitrite is employed. The time required for full conversion of the hydrazide into the azide may vary between 5 to 30 min and can be monitored by spray reagents (see experimental procedure below). 

Of the group VIII metal catalysts, Co has received the most attention. With CojfCOlg, at 180-185 C and CO H2 pressures of 35 MPa, CH3OH gives a product distribution of 38.8% ethanol, 4.7% n-propanol, 9.0% methyl acetate, 6.3% ethyl acetate, 8.5% methane and traces of acetaldehyde, methyl formate, propyl acetate and butanol. At 160-180° and 21 MPa of CO H2, tert-butanol gives a 63% yield of iso-amyl alcohol, and iso-propanol gives 11% of a mixture of n- and iso-butanol. n-Propanol reacts slowly at 180°C. 

The prefix tert is found in ferf-butyl and ferf-pentyl because each of these substituent names describes only one alkyl group. The name ferf-hexyl cannot be used because it describes two different alkyl groups. (In older literature, you might find amyl used instead of pentyl to designate a five-carbon alkyl group.)... 

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