bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pro‐oxidant effects of thiophenes: Sulfur‐dioxide‐catalysed hemolysis of hydroperoxides and oscillating oxidations
Authors: van Tilborg W.J.M. , Smael P. 
Published: September 2010

AbstractIn autoxidizing n‐hexylbenzene traces of SO2, evolved from “inactive” thiophenes or from other SO2 sources, give rise to an oscillating oxidation with oxygen evolution. This entirely new phenomenon is explained in terms of an SO2‐catalysed homolysis of hydroperoxides, which results in a very high initiation level.
Singlet‐oxygen oxidation of thiophenes
Authors: van Tilborg W.J.M. 
Published: September 2010

AbstractSinglet‐oxygen oxidation of alkyl‐ and aryl‐substituted thiophenes has been studied with respect to product formation and relative rates of reaction. The reactivity of thiophenes towards singlet oxygen decreases with the introduction of electron‐withdrawing groups. A comparison of the nature of the products and the relative reactivities towards singlet oxygen of a number of thiophenes with their previously reported anti‐oxidant behaviour indicates that singlet oxygen plays hardly any significant role, if at all, in the desulfurization of thiophenes under autoxidative conditions.
Synthesis of the luteinizing hormone‐releasing hormone (LHRH) by the repetitive excess mixed anhydride (REMA) method
Authors: Beyerman H.C. , Rammeloo T. , Renirie J.F.M. , Syrier J.L.M. , van Zon A. 
Published: September 2010

AbstractUsing ethyl glycinate (I) as starting material, after Nα‐benzyloxycarbonyl‐nitroarginylproline [ZArg(NO2)‐Pro, II]* had been coupled to it with the aid of excess mixed anhydride, and after acidolysis, the tripeptide Arg(NO2)‐Pro‐Gly‐OEt was obtained. By means of the repetitive excess mixed anhydride (REMA) method the protected decapeptide sequence (X) of the luteinizing hormone‐releasing hormone (LHRH) was synthesized (Scheme). In the course of this process, at the heptapeptide stage, the C‐terminal ethyl ester (VIIa) was converted by ammonolysis into the amide (VIIb).Acidolysis of X, with liquid hydrogen fluoride, gave crude LHRH (XI). Purification afforded LHRH, which was chemically identical with the luteinizing hormone‐releasing hormone synthesized elsewhere by another method, and which was found to be highly active biologically.
On the synthesis of 2,5‐dihydrothiophene
Authors: Everhardus R.H. , Gräting R. , Brandsma L. 
Published: September 2010

Abstract2,5‐Dihydrothiophene can be obtained in reasonable yield by reaction of cis‐1,4‐dichloro‐2‐butene with anhydrous sodium sulfide in a mixture of methanol and dimethyl sulfoxide. The contaminating 3,4‐epithio‐1‐butene can be removed by reaction with excess of Na2S. 3,4‐Epithio‐1‐butene and 3,6‐dihydro‐1,2‐dithiin have been obtained in good yields by treating trans‐1,4‐dibromo‐2‐butene and cis‐1,2‐dichloro‐2‐butene with Na2S and Na2S2, respectively.
Derivatives of meta‐di‐tert‐butylbenzene. Part III: Preparation of some chlorinated derivatives
Authors: de Koning Adrianus Jan 
Published: September 2010

AbstractThe preparation of a number of chlorinated derivatives of meta‐di‐tert‐butylbenzene from 3,5‐di‐tert‐butylacetanilide and from 3,5‐di‐tert‐butylbenzoic acid is described.
Reversible binding of sulfur dioxide by polymer‐bound 1,3‐diene acceptor systems
Authors: Nieuwstad Th. J. , Kieboom A.P.G. , Breijer A.J. , van der Linden J. , van Bekkum H. 
Published: September 2010

AbstractIn connection with the removal of sulfur dioxide from waste and flue gases the use of polymer‐bound 1,3‐diene systems has been investigated. Using divinylbenzene/styrene copolymers as the solid support, a number of immobilized 1,3‐dienes were prepared; these were able to bind sulfur dioxide by the formation of the corresponding sulfolene systems. Heating of the latter resulted in liberation of sulfur dioxide with the concomitant recovery of the original 1,3‐diene system. In most cases, upon repeated use of the polymer‐bound 1,3‐dienes, a decrease of the sulfur dioxide binding capacity was observed. Probably, inter‐chain reactions of the diene groups are responsible for this phenomenon.
A facile and stereoselective approach to geminal endo‐iodo‐exo‐bromocyclopropanes; application in the synthesis of medium‐sized rings
Authors: Loozen Hubert J. J. , Robben Wil M. M. , Buck Henk M. 
Published: September 2010

AbstractGeminal dibromocyclopropanes annelated to six‐, seven‐ or eight‐membered rings can be converted easily to their geminal endo‐lithio‐exo‐bromo derivatives when treated with butyllithium at −95°. Upon reaction of these derivatives with iodine at −95° the corresponding geminal endo‐iodo‐exo‐bromocyclopropanes are obtained in good yields. The structure assignments are made by means of some silver ion‐assisted ring expansions.
Preparation and photochemical electrocyclic reactions of quinoid γ‐oxo‐α,β‐unsaturated esters. Rearrangements to α‐alkoxy‐γ‐lactones
Authors: Mosterd A. , de Noten L. J. , Bos H. J. T. 
Published: September 2010

AbstractA phenyl‐substituted γ‐oxo‐α,β‐unsaturated ester (3) was prepared by photochemical (2 + 2)‐cycloaddition of phenanthrenequinone (PQ; 1) to 1‐ethoxy‐2‐phenylethyne (2). A methyl substituted γ‐oxo‐α,β‐unsaturated ester 5 was prepared by boron trifluoride catalysed addition of PQ to 1‐methoxy‐1‐propyne (4). The γ‐oxo‐α,β‐unsaturated esters 3 and 5Z were rearranged to α‐alkoxy‐γ‐lactones 8 by a photochemical [4 + 2]‐electrocyclic reaction. Silica gel could bring about the same conversion of 5Z to 8.
Synthesis of thiophene‐containing steroid‐like molecules via olefinic cyclization reactions
Authors: Corvers A. , van Mil J. H. , Sap M. M. E. , Buck H. M. 
Published: September 2010

AbstractRing closure of 2‐methyl‐5‐(2‐thienyl)‐2‐pentene (4a) and 2‐methyl‐5‐(3‐thienyl)‐2‐pentene (4b) to the corresponding 4,5,6,7‐tetrahydrobenzo[b]thiophenes 5a respectively 5b, is described. In order to establish the possibility of the direct synthesis of steroids in which the A‐ring is replaced by thiophene, 2‐[6‐(2‐thienyl)‐(Z)‐3‐hexenyl]‐3‐methyl‐2‐cyclopenten‐1‐ol (9a) and its (3‐thienyl)‐substituted analogue (Z)‐ and (E)‐isomers 9b and 9c respectively, were prepared. The (Z)‐isomers failed to give tetracyclic compounds in contrast to 9c which furnished compound 14 in moderate yield.
Studies on polypeptides XX: Synthesis and biological activities of some des‐aspartylangiotensin II analogues
Authors: van Batenburg O. D. , de Graaf J. S. , Kerling K. E. T. , Havinga E. 
Published: September 2010

AbstractReported are the syntheses and the biological activities of (des‐Asp1)‐angiotensin II analogues (heptapeptides) in which the amino terminal arginine moiety is replaced by the following residues: L‐alanyl, D‐alanyl, L‐2‐amino‐4‐pentynoyl, D‐2‐amino‐4‐pentynoyl, glycyl, L‐2‐aminobutyryl and D‐2‐aminobutyryl. The results confirm the previously suggested hypothesis on the influence of the flexibility of the side chain on biological activity when the otherwise predominating terminal guanidino group is absent or replaced by an amino group.
The chemistry of small ring compounds. Part 37. Elimination of cyclopropanone from a tetraheteracyclooctanetetraspirocyclopropane (“SONO”)
Authors: Jongejan E. , van Tilborg W. J. M. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractBis(1‐hydroxycyclopropyl)methylamine 1 and bis(1‐hydroxycyclopropyl) sulfide 2 give on heating at 60° by dehydration the heteracycloalkanetri‐ and ‐tetraspirocyclopropanes SON and SONO (cf. Scheme 2). The total yield of these products is about 80%, whereas the yield of the heterocycles formed from 1, containing only N and O hetero atoms, remains below 10% (cf. Scheme 1). The compound SON is formed by elimination of cyclopropanone from SONO, presumably via S‐protonated SONO.
Novel pyrromethenes. 1‐Oxygen and 1‐sulfur analogues; evidence for photochemical Z‐E isomerization
Authors: van Koeveringe J. A. , Lugtenburg J. 
Published: September 2010

AbstractPyrromethenes [2‐(2‐pyrrylmethylene)‐2 H‐pyrroles] and 1‐oxygen and 1‐sulfur analogues with a minimum number of alkyl substituents can be synthesized under very mild conditions. Even the parent unsubstituted pyrromethene system can be prepared this way. After synthesis in the dark a Z‐configuration was established using N.O.E. measurements. A photochemical Z—E isomerization was detected (PMR spectroscopy) for derivates lacking an intramolecular hydrogen bridge.
A novel bromination for an unsaturated α‐anion ester. Synthesis of 2‐bromo‐cis‐8,cis‐11,cis‐14‐eicosatrienoic acid
Authors: van der Wolf Lodewijk , Pabon Henk J. J. 
Published: September 2010

AbstractElectrophylic bromination via α‐anion esters (ester enolates) of polyunsaturated carboxylic acids has been achieved by the use of diethyl dibromomalonate as a mild source of positive bromine.2‐Bromo‐cis‐8,cis‐11,cis‐14‐eicosatrienoic acid has been prepared, in 27% yield via the tert‐butyl ester. Final purification of the acid could be successfully attained only after application of ion‐exchange chromatography on DEAE‐cellulose.
A nuclear magnetic resonance spectroscopic study of ternary aqueous solutions. The use of bis(methylsulfonyl)methane as a probe for solute‐solvent interactions
Authors: Karzijn Willem , Engberts Jan B. F. N. 
Published: September 2010

AbstractThe present work reports chemical shift measurements fort‐BuOH/H2O, dioxane/H2O, CH3CN/H2O, THF/H2O and DMSO/H2O as well as for aqueous solutions ofn‐Bu4NBr and KBr containing bis(methylsulfonyl)methane (1) as a probe for solute/solvent interactions. For each ternary mixture the behaviour of the water resonance [v(H2O)] and the methylene proton chemical shift [v(CH2)] of 1 is given as a function of solvent composition. The trends ofv(H2O) are not affected by the presence of 1. Furthermore, the direction of the solvent‐induced shift ofv(CH2) in the water‐rich range is no general measure for the change in the solvent structural integrity. The shifts ofv(CH2) are determined by polar interactions (involving 1 as a hydrogen bonding donor as revealed by C‐D stretching frequency shifts for 1‐d2) and nonpolar interactions (including hydrophobic bonding). For dioxane/water especially there is strong evidence for preferential solvation of 1 by the apolar organic cosolvent. The data clearly reveal the complex features of aqueous ternaries. The solvent effects onv(CH2) are discussed in combination with kinetic and thermodynamic data for some slow proton transfer reactions. For DMSO/H2O thev(H2O) values at various mole fractions of water are linearly correlated withCox's data for the free enthalpies of transfer of a series of solutes from water to the corresponding DMSO/H2O mixtures.
Recueil des Travaux Chimiques des Pays‐Bas Journal of the Royal Netherlands Chemical Society: The adsorption of carbon monoxide and carbon dioxide in calcium‐exchanged zeolite Y
Authors: Michelena J. A. , Peeters G. , Vansant E. F. , de Bièvre P. 
Published: September 2010

AbstractAdsorption of CO and CO2 has been studied on zeolite Y in which Na+ ions have been partially exchanged for Ca2+ ions. Physisorption of CO and CO2 provides a sensitive method for the observation of the population of Na+ and Ca2+ ions in supercage positions. The results indicate that Ca2+ ions introduced into a NaY zeolite by aqueous ion exchange preferentially enter sites in the small cavities on subsequent dehydration. When the degree of Ca2+ exchange stays below 35%, all the Na+ ions initially present in the small cavities as well as the incoming Ca2+ ions seem to remain inaccessible for CO and CO2 molecules.However, a Na+ replacement of 35 to 45% leaves the Ca2+ ions unaffected by CO and CO2 but causes an important migration of inaccessible Na+ ions to accessible supercage positions. Further exchange (>45%) results in Ca2+ ions occupying locations exposed to the supercages. This work establishes that CO and CO2 are very sensitive probe molecules for investigating the location of unshielded mono‐ and divalent cations in zeolites.
Preparation of sulfines by chlorination of dithiocarboxylic esters
Authors: Veenstra G. E. , Bronold N. M. , Smits J. F. M. , Tangerman A. , Zwanenburg B. 
Published: September 2010

AbstractA new and simple method for the conversion of the highly substituted arenedithiocarboxylates 1a‐d into the corresponding sulfines (thione oxides) 3a‐d by chlorination and subsequent hydrolysis is described.The geometrical isomers of these sulfines are formed in the ratio 1:1. An excessive chlorination of the unhindered dithioesters 1e‐i results in (α,α‐dichloroaryl) sulfenyl chlorides 4, which can be converted into either thiobenzoyl chlorides by treatment with triphenylphosphine, or chlorosulfines by reaction with water and pyridine. Also an improved preparation of dichlorosulfine is described.
Dieckmann cyclisations in the synthesis of functionalised decalins
Authors: Peterse A. J. G. M. , de Groot Ae. 
Published: September 2010

AbstractReaction of ethyl 1‐methyl‐2,6‐dioxocyclohexanepropionate (8) with LiC=C‐OEt gives, after a rearrangement and an acetalisation, a cyclohexane derivative with a saturated and an unsaturated ester side‐chain (3). This diester can be cyclised in good yield to ethyl 5,5‐(ethylenedioxy)‐4a‐methyl‐2‐oxo‐3,4,6,7,8‐pentahydro‐1‐naphthalenecarboxylate (14).
Reaction of secondary N‐1‐(2‐chloroalkylidene)amines with lithium tetrahydridoaluminate: Synthesis and rearrangement of 1,2,2‐trisubstituted aziridines
Authors: de Kimpe Norbert , Verhé Roland , de Buyck Laurent , Schamp Niceas 
Published: September 2010

Abstract1,2,2‐Trisubstituted aziridines have been prepared by reduction of secondary N‐1‐(2‐chloroalkylidene)amines with lithium aluminium hydride. N‐Substituted 1‐azaspiro[2.5]octanes (spiroaziridines) have been synthesized by this method. Under appropriate gas chromatographic conditions, 1,2,2‐trisubstituted aziridines underwent rearrangement to the corresponding secondary N‐1‐(alkylidene)amines. The reaction mechanisms are discussed.
The chemistry of small‐ring compounds. Part 38. The transient existence of 1‐(p‐anisyl)cyclopropyl cation
Authors: van der Vecht J. R. , Dirks R. J. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractA cyclopropyl cation, stabilized by a p‐anisyl groupAnisyl = methoxyphenyl.
, turns out to be an intermediate in the alcoholysis of 1‐(p‐anisyl)cyclopropyl halides. In other reactions with nucleophiles substitution products are also formed predominantly without ring rupture.The influence of the solvent, nature of nucleophiles and added salts on reaction rates and product distributions support an SN1 type mechanism.
Polyisocyanides 5. Synthesis and polymerization of carbylhistidine and carbylhistamine
Authors: van der Eijk J. M. , Nolte R. J. M. , Drenth W. 
Published: September 2010

AbstractPolymer anchored imidazole functions were obtained by polymerization of carbylhistidine and carbylhistamine. These isocyanides were synthesized from L‐histidine and histamine, respectively. In order to obtain the former isocyanide in optically active form, it was necessary to work at low basicity and to prevent temperatures higher than ambient. Polymerization occurred with 1 mol % nickel chloride and a small amount of trifluoroacetic acid in methanol. The poly(carbylhistidine) showed no optical activity. The apparent pKa of the imidazole function in poly(carbylhistamine) has decreased to 5.2 ± 0.1 compared with free imidazole (7.2), whereas it rises to 9.4 ± 0.2 in poly(carbylhistidine).
The application of levulinic acid as protective group to the synthesis of tetradecaribonucleotide U‐A‐U‐A‐U‐A‐U‐A‐U‐A‐U‐A‐U‐A via the modified phosphotriester method
Authors: van Boom J. H. , Burgers P. M. J. 
Published: September 2010

AbstractAcylation on the 5î‐position of 2î‐O‐methoxytetrahydropyranyl ribonucleosides la (B=U) and 2a (B=Aan) with levulinic acid, followed by phosphorylation of the 3î‐hydroxy function with the monofunctional phosphorylating agent 2,2,2‐trichloroethyl 2‐chlorophenyl phosphoro‐chloridate (3), afforded the fully‐protected mononucleotides 4a and 5a, respectively, in reasonable yields. The latter compounds were key‐intermediates in the synthesis of fully‐protected tetradecaribonucleotide 15a. The preparation of tetradecamer 15a was achieved by using two specific deblocking procedures, i.e. (a) zinc in pyridine/2,4,6‐triisopropylbenzenesulfonic acid to cleave the 2,2,2‐trichloroethyl group and (b) hydrazine in pyridine/acetic acid for the rapid and selective removal of the levulinyl group. Deblocking of the 2‐chlorophenyl groups from 15a was successfully accomplished by the action of fluoride ion. Attention is directed to anomalous reactions occurring with the use of this deblocking reagent.
Acidity and reactivity of some supported molybdenum oxide catalysts
Authors: Ragaini Vittorio , Matarrese Giovanni , Giordano Nicola , Bart Jan C. J. 
Published: September 2010

AbstractThe acidity of MoO3·γ‐Al2O3, MoO3·SiO2, MoO3·SiO2·Al2O3 systems has been determined by measuring the heat of immersion in pyridine; a non‐monotonic variation with the MoO3 percentage has been observed in the range from 0 ‐ 25 wt% MoO3. The extremes are: 4, 8*, 15 and 25* wt % MoO3 on γ‐A2O3; 3,4*, 7, 13*, 16 and 23* wt % MoO3 on SiO2; 1*, 2, 8* and 25 wt % MoO3 on SiO2·Al2O3, where asterisks denote maxima. For the MoO3·Al2O3 and MoO3·SiO2 systems the activity for double‐bond isomerization of 1‐butene has been measured in the temperature range of 200‐245° and apparent activation energies ΔEa have been derived. As a function of the composition, ΔEa shows a minimum for the 14 wt% MoO3·SiO2, a weak maximum (16 wt%) and a steep minimum (8 wt%) for MoO3·Al2O3 catalysts. The selectivity of the isomerisation reaction has been discussed in terms of surface structure and acidity. It is concluded that the formation of various catalytic species rather than the variation of acidity or the deposition of carbonaceous residues accounts for the selectivity of MoO3·Al2O3 and MoO3·SiO2 catalysts towards isomerization of 1‐butene to cis‐ and trans‐2‐butene and therefore for the variation of the apparent activation energy with composition.
The structure of the condensation product of methyl cyanoacetate and 2,4‐dimethoxy‐6‐chloro‐l,3,5‐triazine
Authors: Weber A. J. M. , Huysmans W. G. B. , Mijs W. J. , Bovée W. M. M. J. , Smidt J. , Vriend J. 
Published: September 2010

AbstractFrom NMR and IR measurements it appeared that the title compound occurs in solution in two tautomeric forms, a predominant NH, and an enolised ester form. Both forms are in rapid equilibrium. The structure (I) expected for this type of condensation does not occur. A second exchange process involves breaking of an intramolecular H‐bond combined with rotations about the triazinyl side chain bond.
Synthesis of racemic and optically active codeine and morphine via the N‐formylnordihydrothebainones: (Chemistry of opium alkaloids, part X)
Authors: Beyerman H. C. , van Berkel J. , Lie T. S. , Maat L. , Wessels J. C. M. , Bosman H. H. , Buurman E. , Bijsterveld E. J. M. , Sinnige H. J. M. 
Published: September 2010

AbstractStarting from 3,4,5‐trihydroxybenzoic acid (gallic acid), racemic 1‐(3,5‐dibenzyloxy‐4‐methoxybenzyl)‐1,2,3,4‐tetrahydro‐6‐methoxyisoquinoline (3, Scheme) was synthesized. Resolution with (‐)‐(S)‐malic acid yielded (+)‐(R)‐3. By a Birch reduction, followed by N‐formylation, and by acid‐catalysed cyclization, we obtained racemic and optically active N‐formyl‐2‐hydroxynordihydrothebainone (6). 6 Was selectively converted into N‐formyl‐2‐(1‐phenyltetrazol‐5‐yloxy)nordihydrothebainone (7). Hydrogenolysis of (‐)‐7 and of racemic 7 yielded (‐)‐N‐formylnordihydrothebainone (8) and racemic 8, respectively. Previously we had converted the N‐formyl derivative (8) in various ways into dihydrothebainone. The conversion into (‐)‐codeine and (‐)‐morphine is known.
Steric effects in alkylpyrimidines
Authors: van der Plas H. C. , Koudijs A. 
Published: September 2010

AbstractTreatment of solutions of 4,6‐dimethylpyrimidine and 4,6‐di‐t‐butylpyrimidine in acid with aliphatic acids (RCO2H) in the presence of silver nitrate and ammonium peroxydisulfate gave the 2‐R‐4,6‐dimethyl‐ and 2‐R‐4,6‐di‐t‐butylpyrimidines (R = C2H5, i‐C3H7, t‐C4H9). Ths pKa values of these compounds were measured. It was found that 2,4,6‐tri‐t‐butylpyrimidine is a weaker base than expected by about 1.6 pKa units. Oxidation of 2‐isopropyl‐4,6‐di‐t‐butylpyrimidine with permaleic anhydride gives 2‐isopropyl‐4,6‐di‐t‐butylpyrimidine N‐oxide. Under the same conditions 2,4,6‐tri‐t‐butylpyrimidine could not be converted into the corresponding N‐oxide.
Asymmetric reductions by a chiral pyridine‐dinucleotide model
Authors: van Ramesdonk H. J. , Verhoeven J. W. , Pandit U. K. , de Boer Th. J. 
Published: September 2010

AbstractThe reduction of two activated carbonyl compounds by a chirally substituted 1,4‐dihydronicotinamide system is described. Although the chiral centre is far removed from the reaction centre, a rather high (up to 27%) asymmetric induction is observed. This degree of asymmetric induction is discussed in relation to the ‐ independently documented ‐ differential substrate accessibility of the two diastereotopic faces of the nicotinamide ring.
Topochemistry. Part XL. 1The crystal structures of trans‐1,2‐dibenzoyl‐ and 1,2‐di‐p‐toluylethylene
Authors: Bart J. C. J. , Schmidt G. M. J. 
Published: September 2010

AbstractThe crystal structures of the two title compounds (I and II, respectively) have been solved from partial three‐dimensional data by means of SEARCH, and refined by a full‐matrix least‐squares programme with anisotropic temperature factors of all but the hydrogen atoms to r = 0.042, 0.031, R = 0.078, 0.075.The bond lengths and angles (e.s.d. 0.01 Å, 0.3°) are consistent internally and between the two molecules, as well as with similar values in related molecules.The molecules are centrosymmetric and have adopted the cisoid conformation of the C=C‐C=O group. The benzene rings, and the CC(O)C and CCCC systems are planar, with dihedral angles between these groups of 12.0° (I), 9.7° (II) and 12.6° (I), 4.4° (II).Upon irradiation trans‐1,2‐dibenzoylethylene undergoes a single‐crystal‐single‐crystal transformation to the cis‐isomer.
Convenient methods for the preparation of di(1‐alkynyl) sulfides, sulfoxides and sulfones, and application of the sulfoxides and sulfones in the formation of novel heterocyclic systems
Authors: Verboom W. , Schoufs M. , Meijer J. , Verkruijsse H. D. , Brandsma L. 
Published: September 2010

AbstractDi(1‐alkynyl) sulfides and the corresponding sulfoxides are obtained in high yields from lithium alkynides and sulfur dichloride or thionyl chloride, respectively. The di(1‐alkynyl) sulfoxides and also the corresponding sulfones (prepared by oxidation of di(1‐alkynyl) sulfides with m‐chloroperbenzoic acid) react very rapidly with disodium sulfide, selenide or telluride to form six‐membered heterocyclic compounds.
Force field calculations on some t‐butyl substituted cyclohexane compounds
Authors: van De Graaf B. , Baas J. M. A. , Wepster B. M. 
Published: September 2010

AbstractThe results are reported of empirical force field calculations on conformers of t‐butylcyclohexane, cis‐ and trans‐1,4‐di‐t‐butylcyclohexane and trans‐1,2‐di‐t‐butylcyclohexane using the force fields of Allinger et al. (AFF) and of Schleyer et al. (SFF). Comparisons of energy differences and geometric data with experimental values show that both force fields yield useful results; SFF gives the better correlation. The A value of the t‐butyl group is calculated to be 4.7 kcal mol−1 (19.7 kJ mol−1). Cis‐1,4‐di‐t‐butylcyclohexane and trans‐1,2‐di‐t‐butylcyclohexane are predicted to exist as conformational mixtures. The concept of additivity in the prediction of strain energies is discussed.