Fe/t-Butyl group

SAMPLE SOLUTION (a) The most stable conformation is the one that has the larger substituent, the fe/t-butyl group, equatorial. Draw a chair conformation of cyclohexane, and place an equatorial tert-butyl group at one of its carbons. Add a methyl group at C-3 so that it is trans to the tert-butyl group. 

Figure 11-3 Space-filling models of c/ s- and frans-2,2,5,5-tetramethyl-3-hexene, which show the difference in steric interactions between the fe/t-butyl groups...

The second class of catalysts are zinc(II) mono- or dialkoxides obtained from polyhydric phenols and dialkylzinc with partly polymeric stmctures. This system, extensively studied by Kuran [84], is an optimization of the water/diethylzinc and polyphenol/diethylzinc systems developed by Inoue [85]. The use of soluble zinc phenoxides and their analogous cadmium complexes as catalyst for the copolymerization of CO2 and epoxide was studied extensively by the Darensbourg group [86]. This work focused on the use of mononuclear phenoxide derivatives with bulky substituents, e. g., phenyl- and fe/t-butyl groups, on the aromatic ring to a homogeneous catalytic system and thus enhance the activity of the Zn phenoxides. The catalysts developed are stabilized through ancillary neutral... 

For the c/s-isomer, on the other hand, the most stable chair conformation is also the conformation needed for elimination, with the fe/t-butyl group equatorial and the bromine axial. The c/s-isomer will react much faster than the frans-isomer because the conformation required for elimination is the more stable conformation. 

Sample Solution (a) The molecule has a ferf-butyl group bonded to a nine-membered cycloalkane. It is ferf-butylcyclononane. Alternatively, the fe/t-butyl group could be named systematically as a 1,1-dimethylethyl group, and the compound would then be named (l,l-dimethylethyl)cyclononane. Parentheses are used when necessary to avoid ambiguity. In this case the parentheses alert the reader that the locants 1,1 refer to substituents on the alkyl group and not to ring positions. 

The prefix sec- is short for secondary. A sec-butyl group is formed by removal of a 2° H. The prefix tert- is short for tertiary. A fe/t-butyl group is formed by removal of a 3° H. 

For aryl halides and sulfonates, even active ones, a unimolecular SnI mechanism (lUPAC Dn+An) is very rare it has only been observed for aryl triflates in which both ortho positions contain bulky groups (fe/T-butyl or SiRs). It is in reactions with diazonium salts that this mechanism is important ... 

When substituents are alphabetized, iso- is used as part of the alkyl group name, but the hyphenated prefixes are not.Thus, isobutyl is alphabetized with /, but n-butyl, fe/t-butyl, and sec-butyl are alphabetized with b.The number prefixes di-, tri-, tetra-, etc. are ignored in alphabetizing. 

Highly branched groups such as fe/t-butyl are commonly described as bulky. ... 

The lUPAC rules permit certain common alkyl group names to be used. These include A -propyl, isopropyl, A -butyl, sec-butyl, isobutyl, fe/t-butyl, and neopentyl (Section 2.13). 

The alkyl group to which lithium is bonded is fe/t-butyl, and so the name of this organometallic compound is ferf-butyllithium. An alternative, equally correct name is 1,1-dimethylethyllithium. 

As molecular oxygen can interact favorably with carbanionic centers, the logical conclusion is that complexation of a phenol with Fe(III) in the enzyme, for example, will develop a similar center. Of course, the hindered phenol (11), when complexed with Co (III) as in (12) constitutes a special case in that the bulky t-butyl groups prevent the phenolate or the enolate entity from achieving planarity. Consequently, the negative charge is no longer delocalized as in (24) of Scheme 16 but is rather localized at C-2 in an sp hybridized orbital (25). Nevertheless, molecules of the catechol type, as ene-diols, when bound to the enzyme. 

Another recent example of pendant poly(arylene) is poly(l,3-phenylene) (16c) (Fig. 7) (49). The Pd-catalyzed polymerization of A/-fe7t-butyl-2,4-dibromoaniline and l,3-phenylenebis(trimethylene boronate) gave poly(l,3-phenylene) with the DP of about 18 (GPC) oxidation of pendant secondary fe/t-butyl amine groups to the corresponding nitroxides 5delded polymer 16c with the radical concentration of... 

Oxidative coupling polymerizations represent a general reaction for the preparation of high molecular weight linear polymers from many 2,6-di- and 2,3,6-trisubstituted phenols. When the ortho substituents on the phenols are relatively unhindered alkyl or aryl groups, the poly(phenylene oxide) is the chief product (40,41). Bulky ortho substituents, eg, fe/t-butyl, lead to the formation of... 

The introduction of all l groups at the porphyrin meso positions induces ruffled deformation [9,10,27,28]. A typical example is meso-tetra(te/t-butyl)porphyrin prepared by Smith and coworkers [27,51]. The meso carbon atoms deviate from the mean porphyrin plane upward and downward alternately. The average deviation of the meso carbons in the zinc complex Zn(T BuP) reaches as much as 0.899 A [28], Thus, the iron complexes of this porphyrin such as Fe(T BuP)X and [Fe(T BuP)L2] should be the best model to elucidate the effect of ruffled porphyrin ring on the electronic structure of the iron(lll) complexes. However, the synthesis of Fe(T BuP)X has been unsuccessful until now. For this reason, meso-tetraisopropylporphyrin complexes Fe(T PrP)X, where the meso te/t-butyl groups are replaced by the less bullqr isopropyl groups, have been examined [52,53]. 

The molecule [Fe2(CO)4(CioHis)2] (18) contains two Fe(CO)2 groups held together by a metal-metal bond and by two bridging hydrocarbon ligands." The Fe2(CO)4 unit is planar and perpendicular to the plane of the four acetylenic carbon atoms. The t-butyl groups are bent away from the... 

To provide an internal reference, the solvent is sealed in a capillary, which is placed at the bottom of the NMR tube used for the sample solution. For this purpose, a melting-point capillary is closed at one end and a syringe is used to add the reference solution. For aqueous studies, a 2% solution of t-butyl alcohol in water can be used as reference and as solvent for the paramagnetic solute. The shift with respect to the methyl resonance of the r-butyl group is then monitored. With organic ligands such as acetylacetonate (acac) groups, complexes such as Cr(acac)3, Fe(acac)3, and Co(acac)2 are soluble in benzene and the proton resonance of the solvent is a convenient reference. The capillary is filled one-third full, the lower end of the capillary is cooled in ice, and the upper part is sealed off with a small hot flame. Alternatively, the reference solution can be placed in one compartment of a coaxial pair of cyhndrical NMR tubes, which are available commercially. In either case the spectral display should be expanded to permit an accurate measurement of the frequency shift. 

Although the n bond is used for coordination in all four compounds, the As—As separation (ca 2.36 A) points to retention of double-bond character. A diarsene carrying a Cp Fe(CO)2 substituent in addition to the well known tri(t-butyl)phenyl group has been isolated as a chromium pentacarbonyl complex, 20, from treatment of Cp Fe(CO)2 As(SiMe3)2 with tri(t-butyl)phenylarsenic dichloride and (cyclo-octene)Cr(CO)5. The compound, which is isostructural with the corresponding diphosphene and phospha-arsene, has an As—As separation of 2.259 A and As—Cr and As—Fe distances of 2.492 and 2.387 A, respectively. On the other hand, the As—As distance in [CpFe(CO)2]-(PhAs—AsPh)[(CO)2FeCp] is 2.456 A and the compound is probably best described as a tetrasubstituted diarsine, rather than a diarsene complex . 

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