4- t-Butylcyclohexane

The rates of removal of axial and equatorial protons from 4-t-butylcyclohexane in NaOD/dioxan have been measured by an NMR technique. The rate of removal of an axial proton is 5.5 times faster than for an equatorial proton. What explanation can you offer for this difference ... 

Dimethylbutane 2,2,4-Trimethylpentane 2,2-Dimethylbutane t-Butylcyclohexane n-Octane 2-Propylacetamide t-Butylacetamide, 2-propylacetamide, 2-butylacetamide t-Butylacetamide, t-pentylacetamide, isopentylacetamide t-Butylacetamide, cyclohexylacetamide 2-Octylacetamide, 3-octylacetamide, 4-octylacetamide... 

Energy changes for the conversion of the chair to the boat conformation of the cyclohexane ring can be estimated from a study of the equilibrium between cis- and tra i-l,3-di-t-butylcyclohexane. Some analytical results of Allinger and Freiberg [9] are listed in Table 12.7. 

Hence A (fra .s) = 4117.24kcal/mol for fra .s-l,4-di- -butylcyclohexane and A /(m) = 4113.72kcal/mol for the cis form. These two results are indicative of ring conformation since cA-l,4-di-t-butylcyclohexane is undoubtedly in a twist-boat form while the other is in chair conformation. The spectra of t-butylcyclohexane (in chair conformation) and of rrani-l,4-di- -butylcyclohexane are indeed very similar, except, of course, for carbon 4, which is the same as carbon 1 in the disubstituted molecule, whereas it is similar to the unsubstimted carbons in the monosubstituted cyclohexane. 

Recently, Takenaka et studied a series of base metal catalysts supported on various ceramic oxides for catalytic cracking of kerosene fuel. Yields of H2 and methane from a model kerosene fuel (52 wt% n-Ci2, 27 wt% diethylbenzene and 21 wt% t-butylcyclohexane) over various base metals at 600°C are shown in Figure 33. Ni/Ti02 showed the highest catalytic activity for the cracking reaction of kerosene fuel, and also maintained a better performance for the kerosene feed that contained benzothiophene. However, the catalytic performance of the... 

Isomerization of alkylcyclopentanes or alkylcyclohexanes in which the alkyl group consists of at least two carbon atoms yields methyl-substituted cyclohexanes. For example, at 50°C, sec-butylcyclopentane produced trimethylcyclohexanes but no propylcyclohexane.16 In another study, n-, sec-, or te/t-butylcyclohexanes at 150°C were almost quantitatively converted to tetramethylcyclohexanes.17... 

An axial f-butyl group really is very unfavourable. In c/s-1,4-di-t-butylcyclohexane, one t-butyl group would be forced axial if the compound existed in a chair conformation. To... 

Scheme 11.2 Hydrogenation pathways of 1,2-di-f-butylbenzene to cis- and trans-l,2-di-t-butylcyclohexanes over 5% Rh-C (AcOH room temperature 1 atm H2).

For both terpene ketones, pulegone and camphor, the A ( C-ASIS) has been estimated by a chemical shift comparison method using t-butylcyclohexane as an additional reference compound [409], By comparing the A (ASIS) of both and nuclei it seems that the carbonyl plane rule is also valid for aromatic solvent-induced NMR chemical shifts of carbonyl compounds [409], Obviously, the particular geometrical arrangement of the aromatic solvent molecules around the carbonyl dipole inhu-ences both the and nuclei in the same way. 

Deuterium labelling combined with deuterium decoupling is well known as a method in spectral analysis and in stereochemical and conformational studies. The deuterium-decoupled proton spectra of XCHD.CHDY compounds produced during mechanistic studies are useful for determining the stereochemical course of reactions such as the methoxymercuration of ethylene, (478) the conversion of tyramine into tyrosol, (479) the non-catalytic addition of deuterium molecules to cyclopentadiene, (480) and alkyl transfer and olefin elimination in 2-phenyl-l,2-dideuterioethyl transition metal compounds. (481) The proton spectra of [ H ]- and [ Hg]-t-butylcyclohexanes were... 

Anions (25) derived from aryl and heterocyclic aldehydes have been used by Hunig et al. for the preparation of a large number of ketones in which one residue is aromatic or heterocyclic (equation 9). In view of the competition between displacement and elimination so frequently encountered in reactions of nucleophiles with secondary halides, it is striking that alkylation of (25 R = Ph) proceeds well even with a tertiary iodide. l-Bromo-4-t-butylcyclohexane reacts with (25) to give the trans product (26) with inversion of configuration (equation 10). 

The amount of equatorial conformer present does increase in the order Me < Et < i-Pr < t-Bu, but perhaps not quite as expected. The ethyl group must he physically larger than a methyl group but there is hardly any difference in the equilibrium constants. The increase in the proportion of equatorial conformer on going from Et to i-Pr is only a factor of two but for t-butylcyclohexane, it is estimated that there is about 3000 times more of the equatorial conformer than the axial conformer... 

Acetoxy-2-t-butylcyclohexane 2-t-Butylcyclohexyl acetate o-t-Butylcyclohexyl acetate Cyclohexanol, 2-(1,1-dimethylethyl)-, acetate 2-(1,1-Dimethylethyl)-cyclo-hexanoi acetate 2-(1,1-Dimethylethyljcyclohexyl acetate EINECS 201-828-7 Green acetate Grumex Ortholate Verdox Ylanat ortho. Used in... 

Men who were exposed to a mist of a specific type of Finnish white spirits used for washing cars (Pfaffli et al. 1985) had elevated levels of dimethylbenzoic acid, a metabolite of trimethylbenzene, in their urine following the workshift. This study attempted to quantify exposure to white spirits through the analysis of dimethylbenzoic acid isomers, which are easily detected markers. It assumed that being in a mixture does not affect the metabolism of trimethylbenzene or any of the other constituents of Stoddard solvent. The amount excreted was linearly related to the estimated exposure level. The composition of the white spirits in this study included 11% aromatics with 1% trimethylbenzene isomers, which is similar to the compositions of Stoddard solvent used in the United States. A correlation between exposure to 1,2,4-trimethylbenzene, a component of white spirits, at the TLV- TWA (25 ppm), and the urinary concentration of 3,4-dimethylhippuric acid (3,4-DMHA) was reported in ceramics workers (Fukaya et al. 1994). Rats were dosed by gavage with t-butylcyclohexane (800 mg/kg), another component of white spirits, and seven compounds were identified as urinary metabolites (Flenningsen et al. 1987). The primary metabolite was trans-4-t-butylcyclohexanol, with lesser amounts of 2 "-hydroxy-4t-butylcyclohexanol, 2-methyl-2-cyclohexylpropanoic acid, 2 "-hydroxy- 4 "-t-butylcyclohexanol, 2-methyl-2-cyclohexy 1-1,3-propanediol, 2-hydroxy-4-butylcyclohexanol, and Cis-4-t- butylcyclohexanol also being detected. Rats that had a white spirit formulation (690.8 mg/kg) applied to their tails 5 days/week for 6 weeks were reported to have excreted several products (dimethylbenzoic acid isomers) of trimethylbenzene metabolism in their urine. 

---