Therefore, ΔG o = 0 kcal/mol and K eq = 1. NH 3 B. 2) Polycyclic molecules are common and important in nature. 4 kcal/mol) less stable than the diequatorial conformation. But there is free rotation about the C-C σ. Show all steps of the calculations in your answer. Candeias, Benedicta Assoah, Svilen P. g) Bicyclo [1. Limited time sales will be on daily. The strength of 1,3-syn-diaxial repulsion was evaluated for main types of protecting groups (alkyl, silyl, and acyl) usually used in carbohydrate chemistry. Diaxial refers to the relationship between two substituents that are both in axial positions, but are on opposite sides of the ring. Overview. Not all questions require a written answer. The term coaxial refers to the inner conductor and the outer shield sharing a. Using these values, calculate the energy difference between the axial and equatorial conformations of cyclohexanecarboxylic acid? 1,3-Diaxial Strain (kcal/mol) -OH CỌH -CI -Br -CH₂ 0. The combination of an iridium-phenanthroline catalyst and a dihydridosilane reagent leads to the site-selective functionalization of primary C–H bonds that are proximal to a hydroxyl group. You should find that the trans isomer of 1,4-dimethylcyclohexane is more stable than the cis isomer. 1 -C(CH3)3 2. Corey,* Georgios Sarakinos and Axel Fischer Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA Received 2 August 1999; revised 24. 1. The mechanism studies revealed that a new tetra-substituted vinylidene ortho-quinone methide (VQM) intermediate was likely. 解析：提取完文件信息后可查看预计要扣取的账号流量，部分类型因中转难度有差异而有倍率，如有可能请尽量使用正常倍率的类型。. Its web server is located in Los Angeles, California, United States, with IP address 192. Differential reactivity of 3H-indole styrylcyanines leading to oxazabicyclo[3,3,1]nonanes or N-alkenyl spiropyrans is reported. Only a few diaxial molecular weaves exist-these were achieved by templation with metals. If you were to flip the chair conformation, the tert-butyl would be in the axial position, which destabilizes the conformation. What are 1,3-Diaxial Interactions? Ken Tao is an MCAT expert and explains that these are steric interactions between ring substituents two carbons away in th. In the more stable conformation the. ΔGo = −RT lnKeq (1) (1) Δ G o = − R T ln K e q. Substituent. The most stable isomer for disubstituted cyclohexanes is summarized below. How to use multiaxial in a sentence. 70 0. And this is a much better way to compare the stability of the cycloalkanes. E2, bimolecular elimination, was proposed in the 1920s by British chemist Christopher Kelk Ingold. com is unknown to visit. SiO 2 D. A highly diastereo- and enantioselective methodology for the asymmetric synthesis of vicinal diaxial styrenes and multiaxis system was achieved by organocatalysis. com is 6 years 2 months old. 年底了，是不是要制作各种总结PPT了？插入一段动. Biologically important polycyclic molecules are found in cholesterol, sex hormones, birth control pills, cortisone, and anabolic steroids. Based on this, we can predict that the conformer which places both substituents equatorial will be the more stable conformer. coaxial翻译：同轴的，共轴的, （电缆）同轴的。了解更多。trans-1,2-Dimethylcyclohexane. This student authored video addresses 1,3 diaxial strain in cyclohexane chair structures. With this said, let’s put together the basic unit for naming bicyclic compounds. The distinction between configurational stereoisomers and the conformers they may assume is well-illustrated by the disubstituted cyclohexanes. The lecture deals with:#1,2-diaxial#elimination#cyclohexane#diaxial#elimination#E2#Stereochemistry#Anti-Elimination#ANTI-PERIPLANAR#E2 mechanism#5-membered T. -Make carbon 1 go below plane (flips vertically up and down) -make carbon 4 go above plane (flips vertically up and down) 3. Equatorial position. 4 kcal/mol of torsional strain. Safety status. Alkanes: Calculating the differences in energy between two conformers Part A Using the table, calculate the difference in energy between the two conformers of the compound in the Figure Cost in kcal/mol Interaction CH3-H diaxial CH3-CH3 gauche CH3-CH3 diaxial* iPr H diaxial iPr CH3 gauche iPr-CH3 diaxial 0. Consider the following: The difference in energy between the right- and left-handed chair is 1. 2. (Both have the same orientation). cc,fileboom. 1 At that time, eight products of immediate chorismate (1) and isochorismate (2) origin‡ were known, among them the. Conformation 1 (Diequatorial): In this conformation, both methyl groups are in equatorial positions. Michigan State University. Cyclohexane Conformational Analysis. Unlike E1 reactions, E2 reactions remove two subsituents with the addition of a strong base, resulting in an alkene. net,rapidgator. 2 comments. Spider - Webs, Silk, Predators: Spiders that use silk to capture prey utilize various techniques. The trans -decalin is represented with different drawings but they represent the same molecule viewed at different angles. We have to remember that cis it means "same orientation", so in the axial positions, both methyl groups go up. Having the t-butyl group in an axial orientation on cyclohexanes leads to substantial 1,3-diaxial interactions with hydrogens or other axially-oriented substituents. TABLE 4. Answer: See explanation. The latest Tweets from mykaila dayish (@cxx_mykaila). The first question we must ask is which C the two chlorine substituents are on. Biaxial (BX) geogrid is Tensar's original geogrid invention. Down the A-B bond - place A in the front - pay attention to stereochemistry (5pt). The two axial methyl groups give a total of 3. 9 3. Identify the seven isomers first. trans-1,2- 4. 9 0. The blue and green carbons are in ring A and they are. 3. A DV is often, but not always, similar to one's RDA or AI for that nutrient. We would like to show you a description here but the site won’t allow us. 50 0. Table of Contents. Production and Synthetic Modifications of Shikimic Acid. The rarity of N–N axial chirality calls for development of novelEnantiopure alleno-acetylenic cage (AAC) receptors with a resorcin[4]arene scaffold, from which four homochiral alleno-acetylenes converge to shape a cavity closed by a four-fold OH-hydrogen-bonding array, form a highly ordered porous network in the solid state. 3] 2-isopropylketone effect (1. 2. DVs were developed by the U. 1. daixiala. Final answer. As molecular probes for this study, derivatives of isopropyl 2-O-benzyl-4,6-O-benzylidene-α-d-idopyranoside bearing allyl, acetyl, and tert-butyldiphenylsilyl (TBDPS) protecting groups at O-3 were prepared. Draw cis-1,4-dibromocyclohexane in a chair conformation and determine the approximate strain energy using literature 1,3-diaxial strain energy values. j) Spiro [3. h) Bicyclo [4. Rank them in order of increasing strain. j) Spiro [3. Chair flipping in this compound converts a diaxial conformation into a diequatorial conformation (in contrast to cis-1,2 these are clearly not mirror images). Christian Moessner Fabienne Hoffmann-Emery Jean-Michel Adam Serena Fantasia Dan Fishlock Roland Meier Georg Wuitschik Hasane Ratni . Actual interaction between the two metal groups introduced into the dye. Diauxic growth, diauxie or diphasic growth is any cell growth characterized by cellular growth in two phases. 9: The E2 Reaction and Cyclohexane Conformation is shared under a CC BY-NC-SA 4. Actual confirmation of sis 13 die mental cycloA consistent and comprehensive quantitative framework of the cells in the human body could benefit many areas of biology. For now, I want to discuss 1,3- dichlorocyclohexane. Expert Answer. Allylic strain (also known as A1,3 strain, 1,3-allylic strain, or A-strain) in organic chemistry is a type of strain energy resulting from the interaction between a substituent on one end of an olefin (a synonym for an alkene) with an allylic substituent on the other end. Download : Download full. ¿Por qué se llama interacciones 1/3 diaxiales?Chemistry questions and answers. At the same time, the lone pair of the oxygen also acts as a nucleophile attacking one of the carbon atoms of the alkene. 9 0. , Consider the four isomers of 1‑ethyl‑4‑isopropylcyclohexane in a chair conformation. On. At carbon four, down. The two-dimensional analog is concentric . In the last post we saw that adding a methyl group to cyclohexane results in two chair conformers that are unequal in energy. Daixiala. Chemistry questions and answers. 解析文档. The ortho ester Claisen rearrangement of trisubstituted allylic alcohols exhibits significant levels of diastereoselection. TL;DR Torsional strain can be thought as the repulsion due to electrostatice forces between electrons in adjacent MOs. com | expired domain. ll. Draw a Newman projection for the most stable confirmation of the following systems. Decalin is a bicyclic-saturated hydrocarbon (bicyclo [4. Audience. 1,3-diaxial interactions occur when the substituent is axial, instead of equatorial. Methylcyclohexane (cyclohexylmethane) is an organic compound with the molecular formula is CH 3 C 6 H 11. HÓA HỌC LẬP THỂ Hiện tượng một công thức phân tử ứng với 2 hay nhiều chất khác nhau được gọi là hiện tượng đồng phân. Hydrogen and chlorine atoms and methyl and tert. 3 kJ/mol) relative to the conformer where methyl is axial. Spider - Webs, Silk, Predators: Spiders that use silk to capture prey utilize various techniques. The meaning of MULTIAXIAL is occurring along or operating in more than one axis. Conformational analysis can be used to predict and explain product (s. (Click on the groups themselves, not on bonds. Axially chiral scaffolds have gained increasing interest in the past decades owing to their profound applications as chiral ligands and oganocatalysts 1,2,3,4,5,6,7,8,9,10,11,12,13. Decalin is used mostly as a solvent. [Pg. The trans-diaxial 1,6-diol of 3,4-di-O-all. And carbon six, down. Then draw all six axial bonds and six equatorial bonds on each. me,youtube. It has parallel (paraxial) fangs, and. 中转：大多数类. 多くの化合物は構造的に類似した6員環を有しているため. A Numerical Ranking Of “Bulkiness” For Cyclohexane Substituents. In the more stable conformation the. For 8 and 11. [citation needed] It has a wire conductor in the centre (D), a circumferential outer conductor (B), and an insulating medium called. 3. 1: E3. Question: A B Calculate the energy due to 1,3-diaxial strain for both conformations A and B : - H−CH3:3. Clear the screen (file/new) and use the cyclohexane template to start. The conformation shown in the video is the most stable because the bulkier group, the tert-butyl group, should be put in the equatorial position as it is a bigger problem when dealing with steric hindrance. The most stable conformation of cis-1-tert-butyl-4-ethylcyclohexane and strain in the chair form is-. 1,3-Diaxial Interaction Explained: Chair conformations are commonly used to describe the various interactions between atoms on cycylohexanes. Скриншот для Daixialaom скоро будет здесь. Using these values, calculate the energy difference between the axial and equatorial conformations of bromocyclohexane? HY 1,3-Diaxial Strain (kcal/mol) -CH3 0. 💓 insta: love. Elimination Reactions Just as there are two mechanisms of substitution (S N 2 and S N 1), there are two mechanisms of elimination (E2 and E1). In examining possible structures for substituted cyclohexanes, it is useful to follow two principles: (i) Chair conformations are generally more stable than other possibilities. The predictable and modular assembly of complex molecular structures is one of the main challenges in synthetic organic chemistry, which therefore necessitates the development of new synthetic. 5 kcal/mol) cooperate with each other in the aa conformer (6) with respect to the ee conformer (5)—so much so that in a solvent of low polarity, e. Обновлен последний раз : 4 года назад. However, to use cycloalkanes in such applications, we must know the effects, functions, properties, and structures of cycloalkanes. accidental discovery. This set of Organic Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Stereochemistry”. 5 degree. Cyclohexanone monooxygenase, 60 on the cyclohexane catabolic pathway, is the prototype of a flavin-dependent Baeyer-Villiger oxygenases 61 and is the most extensively studied system. Correct option is D) The stable conformers of trans-1,4-dimethyl cyclohexane is 1-equatorial-4-equatorial form. Cis -1,2-di methyl cyclohexane exists as a pair of chair conformations, which are in ring flip equilibrium . 9: The E2 Reaction and Cyclohexane Conformation is shared under a CC BY-SA 4. In this case, let's sketch the butadiene in this way. So here we have a cyclohexane ring. Draw the two chair conformations of trans-1,4-dibromocyclohexane and. For the substituted cyclohexane compound shown, identify the atoms that will sterically interact with the methyl group 1,3-diaxial fashion. Conformer with equatorial Strain (chemistry) In chemistry, a molecule experiences strain when its chemical structure undergoes some stress which raises its internal energy in comparison to a strain-free reference compound. 7 0. 2. 8 kJ/mol. Conformational analysis. 8 kJ/mol. Lastly, the two rings can be joined with a singe bridge head carbon. 0 kJ/mol. Elimination Reactions Just as there are two mechanisms of substitution (S N 2 and S N 1), there are two mechanisms of elimination (E2 and E1). Page ID. These two conformational structures are the result of chair-chair interconversions, and are both chiral. Based on the table above, trans -1,2-disubstitued cyclohexanes should have one chair conformation with both substituents axial and one conformation with both substituents equatorial. 若遇到连接异常. 06 kcal mol −1) than 1ee1, which means that the IAHB effect is slightly larger than the 1,3-diaxial steric effect. 6 kcal/mol. 90 -CH₂CH3 0. Calculate the strain in the diequatorial conformation of cis-1,3dimethylcyclohexane. com has an estimated worth of US$ 35,629, based on its estimated Ads revenue. Heterocyclic Compounds. com has Alexa global rank of 484,092. Three new dibenzo-α-pyrone derivatives, alternolides A–C (1–3), and seven known congeners (4–10) were isolated from the marine-derived fungus of Alternaria alternata LW37 assisted by the one strain-many compounds (OSMAC) strategy. Page ID. Between 1922 and 2015 there were 1 birth of Daixiang in the countries below, which represents an average of 0 birth of children bearing the first name Daixiang. The structure of. The simplest imaginable conformation for cyclohexane, the planar one, is not only not the ground state conformation, it is so high in energy that it plays no part in the conformational analysis of cyclohexane . It is a domain having com extension. 8 mathrm{~kJ} / mathrm{mol}(0. com information at Website Informer. On carbon-2: cis or trans -1,2-dimethylcyclohexane. [Pg. In E allylic alcohols, a 1,3-diaxial interaction develops in the chairlike transition state leading to the anti isomer, rendering the reaction syn selective by a factor of 3−5 to 1. Page ID. Di equatorial : A pair of atoms or groups that are both in an equatorial position on a cyclohexane ring. 3. 3 kJ/mol) of energy to have a methyl group in the axial position compared to the equatorial position. Given that the free energy of the twist-boat conformer of cyclohexane is 5. 90 -CH₂CH₂ 0. VIDEO ANSWER: they want us to determine approximately how much Sterk strain does. Stanley F. 6 kJ/mol Which configuration A or B is more stable? Are the methyl and isopropyl groups cis- or trans- to each other? Are the alcohol and isopropyl groups cis-or trans-to each other?A table providing 1,3-diaxial interactions of a variety of substituents with a single hydrogen atom. This chapter emphasizes the important aspects of steric and stereoelectronic effects and their control on conformational and reactivity profiles. Expert Answer. When a substitutent is present at axial position, the conformer will be less stable because it has 1, 3 diaxial interaction which is a steric interaction of axial group. y=ln (x-4)-2 y = ln(x−4)−2. Let’s start with the E2 mechanism. Data for disubstituted cyclohexanes Two methyl groups Distance. The energies of axial and equatorial fluoro-, chloro-, and bromocyclohexanes as well as diaxial, axial−equatorial, and diequatorial 1,2-, 1,3-, and 1,4-dihalocyclohexanes were calculated using the hybrid density functional methods B3LYP and B3P86 as well as MP2 and QCISD and the 6-311G* and 6-311+G(2df,p) basis sets. dǎ xiǎng. As for the iridium-catalyzed asymmetric allylic substitution process, cinnamyl carbonate analogs 1 were well tolerated, enabling the efficient production of a series of compounds 3 with high enantioselectivities (96%–98% ee) (Figures 2, 3a–3m). Factor the difference of two squares. 解析文档. Solution. Background. 2, 3, 4 The same product is expected from both. 0 -CH (CH3)2 4. This geogrid changed the game when it was first introduced for soil stabilization back in the 1980s. Question: Which of the following substituents would produce the greatest amount of 1,3 diaxial strain when substituted for Cl in the following structure? CO2H CN OH H C (CH3)3. To better understand how this works, let’s take a look at this board. A table providing 1,3-diaxial interactions of a variety of substituents with a single hydrogen atom. The “1,3” describes the distance between the substituent and hydrogens that are in axial position. CH Cauche Ant 2. Order Araneida (Araneae) has more than 46,700 species in about 110 families. Chemistry questions and answers. Pharmacology. net dictionary. However, one value for each nutrient, known as the Daily Value (DV), is selected for the labels of dietary supplements and foods. 9 r ^ { 2 } - 25 s ^ { 4 } 9r2−25s4. No single factor is uniquely responsible for the axial preference of a. Name DAIXIANG. 4-47 The diaxial conformation of cis-1,3-dimethylcyclohexane is approxi mately 23 kJ/mol (5. Chair interconversion produces a chair conformation having two ( red ) methyl groups. 7: Bimolecular Elimination: E2. Chemistry questions and answers. Question: + A table providing 1,3-diaxial interactions of a variety of substituents with a single hydrogen atom. The invention of a method for the synthesis of 1,3-diols from the corresponding alcohols is described, via controlled, radical-mediated C−H functionalization. However, they are both less stable than trans-CH 3 CH=CHCH 3 (−116 kJ/mol). 9. com receives approximately 6,507 unique visitors each day. Chemistry. Limited time sales will be on daily. Actual interaction between the two metal groups introduced into the dye. 1,3-Diaxial interactions occur in cyclic structures, such as cyclohexane, when two bulky substituents are in axial positions and are eclipsed with each other. Referring to a situation in which two substituents on a cyclohexane ring are both in axial position. Hello students here in this question: we have to explain the 13 dixy interaction we have given the cyclohexene, so it is position 12 and 3. Look at the molecule from the side and see if you can identify the chair structure. Cyclohexane conformation. i) Spiro [5. Question #4: In general, non-hydrogen substituents are more stable when equatorial. 1. The strength of 1,3-syn-diaxial repulsion was evaluated for main types of protecting groups (alkyl, silyl, and acyl) usually used in carbohydrate chemistry. Chair Cyclohexane Tutorial 4. Using the energy values reported in Question 9, calculate the value of the H,R 1,3-diaxial interaction, where R is your chosen substituent. Expert Answer. Elimination of 1-bromo-tert-butylcyclohexane is a prototypical example of how important the anti periplanar relationship is for E2. 8. The transformation. It is a generalized form of tensile testing in which the material sample is simultaneously stressed along two perpendicular axes. Organic Chemistry With a Biological Emphasis by Tim Soderberg (University of Minnesota, Morris) 11. Figure 4. Dayiala offers an array of products including home essentials, kitchen tools, baking tools, makeup tools that help saving time and efforts. 16. Find step-by-step Chemistry solutions and your answer to the following textbook question: Which has a higher percentage of the diequatorial-substituted conformer compared with the diaxialsubstituted conformer: trans-1,4-dimethylcyclohexane or cis-1-tert-butyl-3-methylcyclohexane?. In (−)-menthone [(5) in Fig. The presence of additives such as HMPA or DMPU results in a greater degree of solvation of the. Step 1/2 First, we need to identify the two chair conformers of trans-1,2-dimethylcyclohexane. The axial chirality was constructed via the integration of. com, including its world ranking, daily visitors, bounce rate, average time spent. conformational analysis. Label the Carbons in flipped chair. The two rings can also be connected by a bridge containing one or more carbons to form a bridged bicyclic molecule. 4 kcal/mol less stable than the other. 95 -CH (CH₂)₂ 1. A coaxial cable is a three-dimensional linear structure. For the substituted cyclohexane compound shown, identify the atoms that will interact with the methyl group in a 1,3-diaxial fashion after rotation to the other chair conformation BF. BE BrE HI H A CI HF HG Н. Introduction In 2001, Dosselaere and Vanderleyden described chorismate (1) as a “metabolic node in action” in an outstanding review of the five most important families of chorismate-converting enzymes in microorganisms. Illustrated Glossary of Organic Chemistry. There are many forms of cycloalkanes, such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, among others. A table providing 1,3-diaxial interactions of a variety of substituents with a single hydrogen atom. 8. Conformational analysis. Diequatorial boat formC. 8b09893. A table providing 1,3-diaxial interactions of a variety of substituents with a single hydrogen atom. The hurdle is the lower barriers to rotation compared with that of their biaryl counterparts, rendering their asymmetric synthesis more difficult. A gauche interaction increases the strain in the molecule by 3. Ketamine hydrochloride is a cyclohexane derivative closely related chemically and pharmacologically to phencyclidine, a veterinary anesthetic and drug of abuse (known as angel dust). . Anatomy and Physiology. This is mainly because of the large amount of torsional strain which is present in this form. 2]octane. com receives approximately 6,507 unique visitors each day. (a) Draw both chair conformations of cis-1,3-dimethylcyclohexane and determine which conformer is more stable. According to SiteAdvisor, daixiala. We know that there are two chair conformers of cis-1,3-dimethylcyclohexane, one more stable than the other. Inhibiting the GH activity to alter the glycosylation or catabolism of glycans is an. The stereochemistry of hydrogenating naphthalene is described in Weitkamp’s review. Show all steps of the calculations in your answer. The results of density functional theory (DFT)-based calculations while estimating the values of the 13 C chemical shifts and the spin coupling constants allowed to determine the relative configurations of 1 and 2. Although this is the lowest initial cost geogrid. For methylcyclohexane at room temperature (298 K) the 95:5 ratio of equatorial to axial conformers translates to an energy difference of. The relative stabilities of the cis and trans isomers of disubstituted cyclohexanes depends upon which isomer has the most stable conformer. com: Northern America,United States. A gauche interaction increases the strain in the molecule by 3. daixiala. 09 D and 3. h) Bicyclo [4. The functional classification of joints is determined by the amount of mobility found between the adjacent bones. The conformational equilibria of 3-X-cyclohexanol [X=F (1), Cl (2), Br (3), I (4), Me (5), NMe(2) (6) and MeO (7)] and of 3-X-methoxycyclohexane [X=F (8), Cl (9), Br (10), I (11), Me (12), NMe(2) (13) and MeO (14)] cis isomers were determined from low temperature NMR spectra and PCMODEL calculated c. All the 1,2-dichloro isomers are constitutional isomers of the 1,3-dichloro isomers. daixiala. Question: 7. 3. 1. 4 kJ/mol) = -2. Solve any question of Organic Chemistry - Some Basic Principles and. This makes compound 1 more unstable (higher energy), leading to a faster rate of formation of the carbocation. Question: On the substituted cyclohexane, click on the two groups that are experiencing the largest 1,3-diaxial interaction. Tasks. 3. A value. Decalin. 90 -CH₂CH3 0. Its global rank has gone down by 214,855 positions since 3 months ago. There are 3 steps to solve this one. Having. The six carbon sugar, fructose, in aqueous solution is also a six-membered ring in a chair conformation. Chemistry questions and answers. 1. The ΔE aa–ee values for the cis isomer of compound 1 show that the 1aa1 conformer is slightly more stable (0. ; A chair flip converts all axial groups to equatorial and vice versa (but all “up” groups remain. spider. Browse through a biochemistry textbook and you will see any number of molecules with cyclic structures. Steric strain is the increase in potential energy of a molecule due to repulsion between groups on non-neighbouring carbons. 1. Di equatorial : A pair of atoms or groups that are both in an equatorial position on a cyclohexane ring. Diaxial interaction (1,3- diaxial interaction): An interaction (usually repulsive) between two axial substituents on a cyclohexane ring. Which two chair conformations represent the trans isomers in. trans - and cis -Decalin are fused ring analogs of cyclohexane. 4 kcal/mol. Another effect: 1,3-diaxial interactions are destabilizing. IntroductionThe ring opening of epoxides by water can be either base or acid catalysed and is used extensively for the production of diols. The conformational effects in ethane, butane, cyclohexane, variously substituted cyclohexanes, and cis - and trans -decalins allow a good understanding of the discussions that follow. The 1,1-dichloro isomer is omitted because it is an unexceptional. [1] In the case of limonene, it has been shown that the acid catalysed ring opening of either the cis or the trans isomer leads to the same (trans-diaxial) diol. A table providing 1,3-diaxial interactions of a variety of substituents with a single hydrogen atom. They are non-interconvertible stereoisomers of one another. There are 4 steps to solve this one. The 1,1-dichloro isomer is omitted because it is an unexceptional. 8 1,3-DIAXIAL INTERACTIONS FOR SEVERAL COMMON SUBSTITUENTS SUBSTITUENT 1,3-DIAXIAL. all of the compounds E.