bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanism of the catalytic inhibition of hydrocarbon autoxidation by secondary amines and nitroxides
Authors: Bolsman T. A. B. M. , Blok A. P. , Frijns J. H. G. 
Published: September 2010

AbstractA study has been made of the mechanism of the catalytic inhibition of autoxidation of hydrocarbons at 130°C by secondary amines and derivatives thereof (hydroxylamines and nitroxides). From the effect of hydrocarbon structure on the inhibition and from the various reactions of possible intermediates of the catalytic cycle, it is concluded that alkyl and alkylperoxyl radicals are scavenged alternately. Reaction of an alkyl radical with a nitroxide produces an O‐alkylated hydroxylamine. In the case of tertiary alkyl radicals this hydroxylamine decomposes thermally ‐ via transfer of the β‐hydrogen from the alkyl group to the nitroxide moiety ‐ into olefin and hydroxylamine. The hydroxylamine is subsequently oxidized back to the nitroxide by alkylperoxyl radicals. Kinetic data on the individual steps of the cycle are in accord with the observed inhibiting effect.
Organocuprate induced allylic versus propargylic 1,3‐substitution in sulfinates and sulfonates derived from 3‐hydroxy‐1‐penten‐4‐ynes. Improved synthesis of a precursor for the presumed sex attractant of Acanthoscelides obtectus
Authors: Kleijn H. , Westmijze H. , Kruithof K. , Vermeer P. 
Published: September 2010

AbstractThe sulfinates (E)‐R1‐C≡C‐C(R2, CH=CHR3)‐OS(O)Me (1) have been treated with [R4CuBr]MgX·LiBr (4) in tetrahydrofuran. The ratio allylic versus propargylic 1,3‐substitution in 1, leading to R1‐C≡C‐CR2=CH‐CHR3R4 (2, Z/E ≥ 86/14) and (E)‐R1R4C=C=CR2‐CH=CHR3 (3) respectively, depends on the size of the substituents R1 and R3. As could be concluded from the reaction of (E)‐1 (R1=R2=H, R3= ‐CH(OEt)2) and of the corresponding methanesulfonate (E)‐5 with the heterocuprate [n‐C8H17CuBr]MgBr·LiBr, the ratio 2/3 is also influenced by the nature of the leaving group. A very high regioselectivity has been found if (E)‐5 was reacted with the homocuprate (n‐C8H17)2CuMgBr·LiBr instead of the heterocuprate. The latter reaction is part of an attractive route to the presumed sex attractant of the Male Dried Bean Beetle (Acanthoscelides obtectus).
Conversion of 1‐alkyne‐1‐thiolates and ‐selenolates into thioketene and selenoketene precursors. Preparation of bis(trimethylsilyl)selenoketene, the first stable selenoketene
Authors: Sukhai Ramesh S. , Brandsma Lambert 
Published: September 2010

AbstractLithium 1‐alkynethiolates and ‐selenolates RC≡CXLi (X = S, Se) have been converted with allyl bromide and with 1‐bromo‐2‐butyne into the compounds H2C=CH‐CH2‐X‐C≡C‐R and CH3C≡C‐CH2‐XC≡C‐R (R = t‐C4H9, Me3Si; X = S, Se), respectively. Upon heating, only the sulfides H2C=CH‐CH2‐S‐C≡C‐R gave isolable thioketenes by [3,3]‐sigmatropic rearrangement. The analogous selenoketene and the thioketene from the rearrangement of Me3Si‐C≡C‐X‐CH2CCH3 are unstable.In the reaction of CH3C≡C‐SeSiMe3 and t‐C4H9C≡C‐SeSiMe3 with diethylamine, giving the selenoamides C2H5C(Se)NEt2 and t‐C4H9CH2C(Se)NEt2, the selenoketenes CH3CH=C=Se and t‐C4H9CH=C=Se are the presumed intermediates. Pure bis(trimethylsilyl)selenoketene [Me3Si]2C=C=Se (7) was obtained in 80% yield from the reaction of Me3SiC≡C‐SeLi and Me3SiCl at low temperatures.
Nature of the chemical reaction path
Authors: Fukui Kenichi 
Published: September 2010

AbstractThe importance of orbital concepts in experimental chemistry is stressed in connection with interpreting the nature of chemical reaction paths. The outstanding role of particular orbital interactions is recognized in various elaborate theoretical calculations. Mathematical formulation of the “intrinsic reaction coordinate” is decisively helpful in a quantitative, nonempirical understanding of the characteristic feature of reaction paths and also provides applications to “reaction ergodography” and to the calculation of absolute rates.
Helicenes: A striking temperature dependence in a chemically induced asymmetric photosynthesis
Authors: Vanest J.‐M. , Martin R. H. 
Published: September 2010

AbstractA very high diastereoselectivity is observed when the (‐)‐menthyl ester I is photocyclised at −78°C: (+)98:(‐)2. The ratio is nearly reversed at 80°C: (+)20:(‐)80.
The reversible photochemistry of 1,2‐di‐(2‐naphthyl)cyclopentene
Authors: Wismontski‐Knittel T. , Kaganowitch M. , Seger G. , Fischer E. 
Published: September 2010

AbstractThe title compound 1 undergoes photocyclization to 4a,4b‐dihydrophenanthrene (DHP) derivatives corresponding to two of the three possible conformers 1A, 1B, 1C. The ratio DHPA/DHPB varies with the wavelength of the photoactive light. At lower temperatures only DHPB is formed. DHPA is virtually stable at 25°C, while DHPB decays with a half‐life of 5 × 10−4 s. Both DHP's are oxidized with iodine to the corresponding phenanthrene derivatives. DHPA is strongly fluorescent, it is photo‐oxidized at 436 nm with oxygen even at −150°C. The photoreversion DHPA→1A is inefficient at 25°C and sharply attenuated on cooling. Two modifications of DHPA were observed. This is as expected according to calculations by the CFF‐SCF‐PI‐CI method, which was also used to calculate the geometries and energies of the conformers and the DHP's.
A formalism for the classification and design of organic reactions. I. The class of (− +)nreactions
Authors: Arens J.F. 
Published: September 2010

AbstractA coding system for the classification of organic reactions is proposed. The reacting atoms are considered as points on a cycle and the bonds between these points are indicated by 1, 2, 3 or 0 meaning a single, double, triple or no bond respectively.These bonds change during the reaction. The present paper deals with reactions where the number of points is even and where the reaction changes the bonds in a regular fashion, alternatively diminishing or increasing the bond order with one unit.This class of reactions is denoted as reactions with operator (−+)n. Many reactions of great synthetic utility belong to this class.
The reductive animation of 4‐tert‐butylcyclohexanone with an NADH model
Authors: de Nie‐Sarink M.J. , Pandit U.K. 
Published: September 2010

Abstract4‐tert‐Butylcyclohexanone undergoes reductive amination to a mixture of isomeric 1‐pyrrolidino‐4‐tert‐butylcyclohexanes (3a,b) upon reduction with Hantzsch ester (2), in the presence of pyrrolidine and the corresponding perchlorate. Under standardized conditions (10 equiv. of pyrrolidine, 1 equiv. of pyrrolidine perchlorate), only 75% of the product (3a,b) is formed via reduction by the Hantzsch ester. The remaining 25% is produced in a process which involves a hydride transfer from either the pyrrolidine (secondary amine) or the enamine system, generated as an intermediate in the reaction to the corresponding iminium salt. The stereochemistry of the Hantzsch ester reduction has been investigated by the use of 4,4‐dideutero‐Hantzsch ester (7).
A quantitative study on the relationship between structure and behavioural activity of peptides related to ACTH
Authors: Kelder J. , Greven H.M. 
Published: September 2010

AbstractA series of peptides related to ACTH and MSH with behavioural potencies determined in a pole‐jumping test on rats has been analysed using a modified Free‐Wilson method (Fujita‐Ban analysis). A stepwise multiple linear regression programme was used for the calculation of the individual contributions of the sub‐units to the overall activity. In general a good agreement between calculated and observed potencies was found. This result shows that the use of a model based on independent contributions of the amino acid residues in the peptide chain to the overall biological activity was justified. Inspection of the few exceptions to this rule led to valuable suggestions about spatial interactions at the receptor level.
Photoreactions of ortho‐vinyl triphenylethylenes I. The photochemistry of 1,2‐diphenyl‐1‐(2‐vinylphenyl)ethylene
Authors: Kulyk M. Sindler , Laarhoven W.H. 
Published: September 2010

AbstractIrradiation of the title compound (9) causes two types of photoreactions. endo‐1,6‐Diphenyl‐2,3‐benzobicyclo[3.1.0]hex‐2‐ene**, endo‐(13), is a primary photoproduct resulting from an intramolecular [4 + 2]cycloaddition; it is partially converted into exo‐(13). [2 + 2]Cycloaddition does not occur. This results fits well into the general scheme previously proposed for the photochemical behaviour of o‐vinylstilbenes.The other photoproducts (14‐17) are formed via electrocyclisation reactions occurring in the divinyl‐benzene moiety and in a cis‐stilbene moiety of 9.
Synthesis of phospholipids via phosphotriester intermediates
Authors: Lammers J.G. , van Boom J.H. 
Published: September 2010

AbstractA new phospholipid synthesis has been developed. Phosphorylation of a 1,2 diacylglycerol with the monofunctional reagent R1R2POCl (R1 and R2 being phosphate‐protecting groups) provides a phosphotriester in 70–90% yield. Removal of one protecting group affords a phosphodiester, which is condensed with the required alcohol to a second phosphotriester (70–75% yield, based on the first triester). Subsequently, the other phosphate‐protecting group and, if present, groups protecting other functionalities are split off. Of the protecting groups investigated, optimal results were obtained with R1 = NHC6H5 and R2 = OCH2CCl3. In this way, phosphatidylethanolamine, phosphatidylglycerol, N,N‐dimethylphosphatidylethanolamine and phosphatidic acid were prepared.
Absorption spectra and reaction kinetics of the radical anion, radical cation and OH adduct(s) of 3,5‐dinitroanisole studied by pulse radiolysis
Authors: Tamminga Johannes J. , van den Ende Cornelis A. M. , Warman John M. , Hummel Andries 
Published: September 2010

AbstractPulse radiolysis of an aqueous solution of 3,5‐dinitroanisole (dNA) containing 0.1 mol dm−3 isopropanol results in the formation of the radical anion of dNA by attachment of solvated electrons with a rate constant of 4.2 × 1010 dm3 mol−1 s−1 and by reaction of dNA with the isopropanol radical, (CH3)2COH, with a rate constant of 2.5 × 109 dm3 mol−1 s−1. The absorption spectrum of dNA− is characterised by a maximum at approximately 275 nm (ϵ,≈︁14 × 103 dm3 mol−1 cm−1) with shoulders at 300 nm and 410 nm. The extinction coefficient is less than 100 dm3 mol−1 cm−1 in the wavelength region 500 nm to 600 nm. The anion decays by a second order process the rate of which decreases with increasing pH.Reaction of OH radicals with dNA in an aqueous solution occurs with a rate constant of 4 × 109 dm3 mol−1 s−1 and results in an absorption in the visible region. The absorption can be separated into two components with maxima at 470 nm and 515 nm on the basis of differing decay kinetics at different wavelengths. The absorption with γmax = 470 nm has an additional band which increases into the infra red and is assigned to a complex between the OH radical and the π‐electron system of dNA. The absorption with γmax = 515 nm is assigned to a combination of the four possible cyclohexadienyl type radicals which can result from σ‐bond formation between OH and a ring carbon atom.An absorption with γmax = 480 nm, found on pulse irradiation of a deaerated solution of dNA in cyclohexane, is attributed to the radical cation of dNA. The extinction coefficient of dNA+ is estimated to be 6.0 + 0.6 × 103 dm3 mol−1 cm−1.
Structure and conformation of heterocycles. X. On 1,4,5,8‐tetraazadecalins
Authors: Fuchs Benzion , Ellencweig Aviyakar 
Published: September 2010

AbstractA synthetic, structural and conformational study of 1,4,5,8‐tetraazadecalin (3) and several of its new, substituted derivatives was performed. Mass‐spectrometric and NMR‐spectroscopic data were taken to indicate a trans‐fused double chair in most cases. These findings, juxtaposed to the notorious elusiveness of trans‐1,4,5,8‐tetraoxadecalin (2) were rationalized in terms of a “reverse anomeric effect”. Substituent effects were also assessed: substituents in the two angular positions or on all four nitrogens preclude trans fusion in favour of the isomeric cis‐ and/or biimidazolidin‐2‐yl structures. The cis‐geometry also prevails in systems were it is imposed by bridging substituents.
Synthesis and acid‐ and base‐catalyzed reactions of hexobarbital 1′,2′‐epoxide and heptabarbital 1′,2′‐epoxide
Authors: Bakker B. H. , van der Gen A. , Vermeulen N. P. E. , Breimer D. D. 
Published: September 2010

AbstractThe synthesis of 1′,2′‐epoxides of hexobarbital (1a) and heptabarbital (1b) is described. Epoxide2a(from1a) consists of a mixture of diastereoisomersIandII. Only isomerIIis able to undergo base‐catalysed cyclization with formation of furopyrimidine3a. Epoxide2b(from1b) likewise affords furopyrimidine3b. The chemical behaviour of3aand3bindicates the occurrence of a ring‐opened keto tautomer. Upon treatment with acid, epoxides2a,bundergo cleavage with formation of C5‐alkyl‐substituted barbituric acids7a,b, thus explaining the absence of 1′,2′‐dihydroxy compounds among the metabolites of barbiturates1aand1b.
Reactions of carbon nucleophiles with 4‐phenyl‐ and 4‐tert‐butyl‐5‐halogenopyrimidines. On the occurrence of an SRN1 mechanism
Authors: Oostveen E. A. , van der Plas H. C. 
Published: September 2010

AbstractReaction of 5‐X‐4‐phenylpyrimidine (X = Br, Cl) with the enolate anions of acetone and acetophenone in liquid ammonia yields 5‐acetonyl‐ and 5‐phenacyl‐4‐phenylpyrimidine, respectively. It is shown that these reactions proceed via an SRN1 mechanism. Reaction of 5‐X‐4‐phenylpyrimidine (X = Br, Cl) with the enolate anion of pinacolone gives besides SRN1 substitution, addition of the anion to the N(1)‐C(6)‐azomethine bond. On treatment of 5‐X‐4‐tert‐butylpyrimidine with the enolate anions of acetone, acetophenone or pinacolone, substitution products are formed in very low yields. Addition of potassium to the liquid ammonia or irradiation with near ultraviolet light, however, increases the yields of 5‐substituted 4‐tert‐butylpyrimidine derivatives considerably.
Anomalous effects in measurements of rotational barriers in formamidinium ions. Influence of solvent, counter‐ion and concentration
Authors: Staps R. J. F. M. , Scheeren J. W. , Pijpers F. W. , Nivard R. J. F. 
Published: September 2010

AbstractChemical exchange studies on the tetramethylformamidinium ion lead to anomalous values for the Arrhenius parameters of internal rotation when apolar solvents, high concentrations and nucleophilic anions are used. The deviations cannot be ascribed to ion‐pairing, and might be due to covalent bonding.
Synthesis of the 5′‐triphosphate of a trimer containing 2′‐5′‐internucleotide linked riboadenosines
Authors: den Hartog J. A. J. , Doornbos J. , Crea R. , van Boom J. H. 
Published: September 2010

AbstractStarting from two properly protected building blocks derived from adenosine and two effective phosphorylating agents, a fully protected intermediate containing two 2′‐5′‐internucleotide phosphotriester bonds and one functionalized 5′‐phosphotriester group was prepared. Selective deblocking of one protective group from the 5′‐phosphotriester function, followed by reaction with pyrophosphoric acid and subsequent removal of all protecting groups, afforded the 5′‐triphosphate of a 2′‐5′‐linked trimer of riboadenosine.
A simple synthesis of N,N‐dialkyl‐3‐alken‐1‐yn‐1‐amines
Authors: Verboom W. , Everhardus R. H. , Bos H. J. T. , Brandsma L. 
Published: September 2010

Abstract3‐Alken‐1‐yn‐1‐amines R‐CH=CH‐C≡C‐NR′2, 9 (R = H, Me, R′ = alkyl) have been prepared in good yields by treatment of the Mannich products MeO‐CH(R)‐C≡C‐CH2‐NR′2 ‐ obtained from propargylic ethers MeO‐CH(R)‐C≡C‐H, paraformaldehyde and dialkylamines R′2NH ‐ with strong bases under polar aprotic conditions.
The role of tetraalkylammonium salts in the electro‐reduction of ketones III. Pinacolization and asymmetric induction
Authors: van Tilborg W. J. M. , Smit C. J. 
Published: September 2010

AbstractSeveral alkyl aryl ketones have been electro‐reduced in an aprotic medium in the presence of tetraalkylammonium conducting salts. Quantitative yields of the corresponding pinacols have been obtained, except in cases where steric crowding in the starting ketone hampers the pinacolization. When chiral conducting salts are used considerable levels of enantiomeric excess in the (RS + SR) fractions of the pinacols are achieved.
Synthesis of fragments of human β‐lipotropin, βh‐LPH. Part I. The synthesis of β‐LPH‐(61‐76) and β‐LPH‐(61‐77), i.e. α‐ and γ‐endorphin, respectively
Authors: Bijl W.A.A.J. , van Nispen J.W. , Greven H.M. 
Published: September 2010

AbstractThe synthesis of β‐LPH‐(61–76) and β‐LPH‐(61–77) [i.e. α‐ and γ‐endorphin, respectively] by means of the fragment condensation approach is described.Several of the fragments leading to these two endorphins were also obtained as pure, free peptides.
Interpretation of vicinal proton‐proton coupling constants by a generalized Karplus relation. Conformational analysis of the exocyclic C4′‐C5′ bond in nucleosides and nucleotides: Preliminary Communication
Authors: Haasnoot Cornelis A. G. , de Leeuw Frank A. A. M. , de Leeuw Harry P. M. , Altona Cornelis 
Published: September 2010

AbstractNew values for 3JHH along the C4′‐C5′ bond in nucleosides and nuclsotides are proposed.
Infrarotspektroskopischer Nachweis des Amins HgNH2OH·HgO, das bei der Bildungsreaktion der Millonschen Base in Form des Monohydrates auftritt
Authors: Weber Richard 
Published: September 2010

AbstractDie Bildungsreaktion der Millonschen Base wird infrarotspektroskopisch untersucht. Es gelingt, die Reaktion auf der Stufe des Imin‐Monohydrates abzufangen. Durch Trocknung desselben ist es möglich, zum Amin zu gelangen. Das Amin‐Spektrum wird mitgeteilt. Auch das Diammin konnte hergestellt und dessen Spektrum aufgenommen werden.
An efficient method for the trimethylsilylation of tertiary alcohols
Authors: Visser R. G. , Bos H. J. T. , Brandsma L. 
Published: September 2010

AbstractTertiary acetylenic alcohols have been transformed into the O‐trimethylsilyl derivatives with trimethylsilyl chloride and triethylamine, using catalytic amounts of dimethyl sulfoxide, hexamethylphosphoric triamide, imidazole, or 1,5‐diazabicyclo[5.4.0]undec‐5‐ene. Saturated tertiary alcohols can be trimethylsilylated in the same way.
Regiospecific functionalisation of unsaturated compounds via their dilithio derivatives: Part 1: Reaction of dilithio compounds of 1‐alkynes with epoxides, benzyl halides and trimethylchlorosilane
Authors: Hommes H. , Verkruijsse H. D. , Brandsma L. 
Published: September 2010

AbstractAcetylenes HCCCH2R (R = H, alkyl) have been converted with good yields into their derivatives HCCCH(E)R (E = CH2CHR′OH, CH2Ph, SiMe3) by reaction of the dilithio compound LiCCCH(Li)R with epoxides OC2H3R′ ( R′ = H, Ph), benzyl chloride and trimethylchlorosilane (TMSCI), respectivily.
Synthesis of methyl (E,Z,Z)‐2(or 4 or 6),9,12‐octadecatrienoate and methyl (E,Z,Z)‐2(or 6 or 8),11,14‐eicosatrienoate
Authors: Klok R. , Möhlmann W. M. M. , van der Wolf L. , Pabon H. J. J. 
Published: September 2010

AbstractFor studies into the relationship between their physical properties and chemical structure, several polyunsaturated fatty acids related to (Z,Z,Z)‐6,9,12‐octadecatrienoic acid and (Z,Z,Z)‐8,11,14‐eicosatrienoic acid were synthesized.Methyl (E,Z,Z)‐2,11,14‐eicosatrienoate and methyl (E,Z,Z)‐2,9,12‐octadecatrienoate were prepared by E‐stereoselective coupling of (methoxycarbonylmethylene)triphenylphosphorane with (Z,Z)‐9,12‐octadecadienal and (Z,Z)‐7,10‐hexadecadienal respectively.The synthesis of methyl (E,Z,Z)‐4,9,12‐octadecatrienoate started from 2,7‐octadiyn‐1‐ol which was reduced with lithium aluminium hydride. The (E)‐2‐octen‐7‐yn‐1‐ol thus obtained was coupled with 1‐bromo‐2‐octyne to give (E)‐2‐hexadecene‐7,10‐diyn‐ 1‐ol. This was converted into 1‐chloro‐(E)‐2‐hexadecene‐7,10‐diyne, which via malonic ester synthesis yielded (E)‐4‐octadecene‐9,12‐diynoic acid. Stereospecific hydrogenation and esterification finally afforded the desired compound, from which methyl (E,Z,Z)‐6,11,14‐eicosatrienoate was obtained by chain elongation.Methyl (E,Z,Z)‐6,9,12‐octadecatrienoate was synthesized from 1,4‐dichloro‐(E)‐2‐butene which was converted into (E)‐4‐octen‐7‐ynoic‐7‐ynoic acid. Coupling the latter with 1‐bromo‐2‐octyne, esterification and reduction yielded (E‐4‐hexadecene‐7,10‐diyn‐ 1‐ol. Conversion into the corresponding chloro compound and stereospecific hydrogenation yielded 1‐chloro‐(E,Z,Z)‐4,7,1 O‐hexadecatriene. Malonic ester synthesis finally afforded the desired compound.The synthesis of methyl (E,Z,Z)‐8,11,14‐eicosatrienoate started from 2‐octyne‐1,8‐diol which was reduced with lithium aluminium hydride; the resulting (E)‐octene‐1,8‐diol was converted into 1,8‐dichloro‐(E)‐2‐octene. The latter was coupled with 1,4‐decadiyne to give 1‐chloro‐(E)‐6‐octadecene‐9,12‐diyne, which was hydrogenated stereospecifically. Malonic ester synthesis finally completed the synthesis.
A study of orientation effects of electronegative substituents on vicinal carbon‐proton spin‐spin coupling constants and the correlation of the latter with proton‐proton coupling constants in the individual rotamers of 13CH3‐C(X)1H‐C(Y)1H2 fragments
Authors: Spoormaker Tom , de Bie Marius J. A. 
Published: September 2010

AbstractOrientation effects of electronegative substituents on vicinal carbon‐proton coupling constants are studied in 1,2‐disubstituted propanes and are found to resemble those on vicinal proton‐proton coupling constants. Known relations for the orientation effect of substituents on synclinal proton‐proton coupling constants can be modified so that they yield reasonable values for synclinal carbon‐proton coupling constants.
Empirical force field calculations VI: Exploration of reaction paths for the interconversion of conformers. Application to the interconversion of the cyclohexane conformers
Authors: van de Graaf B. , Baas J. M. A. , van Veen A. 
Published: September 2010

AbstractA method is described for the calculation of reaction paths for the interconversion of conformers by forcing the internal rotation around one or more single bonds. The implementation of the method in a general computer program for molecular mechanics is discussed. It is shown that forcing the average of two or three torsion angles has distinct advantages. Results of calculations on the interconversion of the cyclohexane conformers are presented as an example.
Formation of (η3‐methallyl) and (η4‐butadiene) ligands from (η1‐2‐buten‐1‐yl) coordinated to group IVB metals
Authors: Blenkers J. , de Liefde Meijer H. J. , Teuben J. H. 
Published: September 2010

AbstractThe synthesis and some properties of the novel triallyl compounds Cp*M(CH2CHCHCH3)3 (Cp*=η5‐C5(CH3)5; M=Ti, Zr or Hf ) and the butadiene‐methallyl compounds Cp*M(η4‐butadiene) (η3‐methallyl) therefrom are reported. The compounds are very reactive towards carbon monoxide and other small molecules.
Empirical force field calculations VII. Rotation of the tert‐butyl groups on the chair conformers of tert‐butylcyclohexane, 9‐tert‐butylbicyclo[3.3.1]nonane and cis‐1,2‐di‐tert‐butylcyclohexane
Authors: Baas J. M. A. , van de Graaf B. , van Veen A. , Wepster B. M. 
Published: September 2010

AbstractEmpirical force field calculations indicate the existence of two chair conformers of cis‐1,2‐di‐tert‐butylcyclohexane. The energy difference amounts to 4.82 kJ mol−1 using the Engler force field. Reaction paths for the interconversion of these conformers have been explored by means of the forced rotation of the tert‐butyl groups. Six transition states have been found in a complicated scheme. The barriers to rotation of both tert‐butyl groups are compared with those calculated for an axial and an equatorial tert‐butyl group on the chair conformation of cyclohexane and on position 9 of bicycle[3.3.1]nonane.