According to the guideline, the conformer with the larger substituent in equatorial is more stable because if the large group is axial, a stronger steric strain will be generated and it is less stable. Because the axial is so identify the axial and equatorial hydrogens in a given sketch of the cyclohexane molecule. Join thousands of students and gain free access to 63 hours of Organic videos that follow the topics your textbook covers. In ISIS/Draw, the "up wedge" and "down bond" that I used, along with other variations, are available from a tool button that may be labeled with any of them, depending on most recent use. In trans-1,2-dimethylcyclohexane, one chair conformer has both methyl groups axial and the other conformer has both methyl groups equatorial. explain how chair conformations of cyclohexane and its derivatives can interconvert through the process of ring flip. When one substituent is axial and the other is equatorial, the most stable conformation will be the one with the bulkiest substituent in the equatorial position. Because the axial is so
Based on the table above, cis-1,4-disubstitued cyclohexanes should have two chair conformations each with one substituent axial and one equatorial. When considering the conformational analyses discussed above a pattern begins to form. What is the order of stability of 1/4 Dimethylcyclohexane? We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. For the following please indicate if the substituents are in the axial or equatorial positions. Bonds to non-ring atoms which make only a small angle compared with the plane of the ring are termed equatorial. When you feel the need, look around! Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. 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. Using the 1,3-diaxial energy values given in the previous sections we can calculate that the conformer on the right is (7.6 kJ/mol - 2.0 kJ/mol) 5.6 kJ/mol more stable than the other. Draw the two chair conformations for cis-1-ethyl-2-methylcyclohexane using bond-line structures and indicate the more energetically favored conformation.
2) AE/EA: Each chair conformation places one substituent in the axial position and one substituent in the equatorial position.
Because the axial is so much more torsionally strained with these H's here. Concept #1: Axial or Equatorial: Which position is better? The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. It's terrible. Equatorial groups are approximately horizontal, but actually somewhat distorted from that (slightly up or slightly down), so that the angle from the axial group is a bit more than a right angle -- reflecting the common 109.5 o bond angle. How do you know which Stereoisomer is more stable? To Determine Chair Conformation Stability, Add Up The A-Values For Each Axial Substituent.
Axial bonds alternate up and down, and are shown "vertical".
Even without a calculation, it is clear that the conformation with all equatorial substituents is the most stable and glucose will most commonly be found in this conformation.
When one substituent is axial and the other is equatorial, the most stable conformation will be the one with the bulkiest substituent in the equatorial position. When faced with the problem of trying to decide which of two conformers of a given disubstituted cyclohexane is the more stable, you may find the following generalizations helpful. When one substituent is axial and the other is equatorial, the most stable conformation will be the one with the bulkiest substituent in the equatorial position. WebEach position has one axial. So the lowest energy conformer is the one where the most substituents are in equatorial position. Because diastereomers have different energies, one form is more stable than the other. However, do I prioritize Cl over the methyl- and isopropyl-group or are the two groups more prioritized due to them being bonded Enter your friends' email addresses to invite them: If you forgot your password, you can reset it.
Now this would become equatorial over here. Equatorial groups are approximately horizontal, but actually somewhat distorted from that (slightly up or slightly down), so that the angle from the axial group is a bit more than a right angle -- reflecting the common 109.5. The more stable conformer will place both substituents in the equatorial position, as shown in the structure on the right. Draw the most stable conformation for trans-1-ethyl-3-methylcyclohexane using bond-line structures. In fact, if you want to think about the equatorial position, it kind of looks like its the equator of the earth. If you flip your chair, you also wind up flipping positions. Aside from drawing the basic chair, the key points are: When a substituent is added to cyclohexane, the ring flip allows for two distinctly different conformations.
Look how far apart they are. Substituents of carbons in the chair confirmation can exist in an axial or equatorial orientation. We've got these ones on the positions and I just want to analyze the ones at the top. This energy diagram shows that the chair conformation is lower in energy; therefore, it is more stable. Thus, a ring-flip that leads to the larger group being oriented equatorially is more energetically stable since the largest group now avoids these interactions. 4: Organic Compounds - Cycloalkanes and their Stereochemistry, { "4.01:_Naming_Cycloalkanes" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.
Practice: Draw the MOST STABLE conformation of cis-1-tert-butyl-4-methylcyclohexane. Because this process is rapid at room temperature, methylcyclohexane is a mixture of two conformational diastere- omers (Sec. Axial bonds are the bonds that form an 90 angle with the ring plane whereas equatorial bonds are the bonds that only make a small angle with the plane. 18 - Reactions of Aromatics: EAS and Beyond, Ch. Since there are two equivalent chair conformations of cyclohexane in rapid equilibrium, all twelve hydrogens have 50% equatorial and 50% axial character. 1) Draw two conformations of cyclohexyl amine (C6H11NH2). So you guys can really see what's going on here. 3. Legal. Each carbon has an axial and an equatorial bond. Each carbon has one axial.
Equatorial groups are approximately horizontal, but actually somewhat distorted from that (slightly up or slightly down), so that the angle from the axial group is a bit more than a right angle reflecting the common 109.5o bond angle. Note, in some cases there is no discernable energy difference between the two chair conformations which means they are equally stable. And then which of them do you think is going to be the most tight together? This position is awesome. It provides templates for various 6-ring chair structures from the Templates menu; choose Rings. Then looking at the "up" bond on each carbon in the cyclohexane ring they will alternate axial-equatorial-axial ect. Make certain that you can define, and use in context, the key terms below. There will be three of each type. Hint: If you dont know what neopentyl is, its ok. Obviously it has 5 carbons, so keep that in mind when deciding equatorial preference! Because the axial is so What that means is that the ring is always going to flip in order to accommodate the preference of the largest substituent. The axial Cl is favored as leaving group because of the elimination reaction mechanism. When one substituent is axial and the other is equatorial, the most stable conformation will be the one with the bulkiest substituent in the equatorial position. Example #1: Draw the following chair in the most stable conformation. Why? The latter is more stable (and energetically favorable) than the former. Each face alternates between axial and equatorial bonds.
Each carbon has an axial and an equatorial bond. So lets get right into it. Draw the most stable conformation for trans-1-t-butyl-4-methylcyclohexane using bond-line structures. At each position, one substituent is axial (loosely, perpendicular to the ring), and one is equatorial (loosely, in the plane of the ring). The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot.
It is also a completely staggered conformation, and is therefore free of torsional stress. A similar conformational analysis can be made for the cis and trans stereoisomers of 1,3-dimethylcyclohexane. All of these systems usually form chair conformations and follow the same steric constraints discussed in this section. Draw the most stable conformer of glucose by putting the OH groups and hydrogens on the appropriate bonds in the structure on the right. The more stable conformation has the large chloro group equatorial. 4. WebA conformation in which both substituents are equatorial will always be more stable than a conformation with both groups axial. Each program has more options for drawing bonds than discussed here. That one is facing up, that axial. Based on this, we can surmise that the energy difference of the two chair conformations will be based on the difference in the 1,3-diaxial interactions created by the methyl and chloro substituents. In fact, over 99% of this compound is going to exist in the equatorial position and less that 1% is going to exist in the axial position. Substituents of carbons in the chair confirmation can exist in an axial or equatorial orientation. Whereas, the equatorial positions they've got all this room to spread out. When the methyl group in the structure above occupies an axial position it suffers steric crowding by the two axial hydrogens located on the same side of the ring.
Substituents of carbons in the chair confirmation can exist in an axial or equatorial orientation. Because the methyl group is larger and has a greater 1,3-diaxial interaction than the chloro, the most stable conformer will place it the equatorial position, as shown in the structure on the right.
There is more room in the equatorial positions (not easily seen with these simple drawings, but ordinary ball and stick models do help with this point). It typically best not to try and directly inter convert the two naming systems. Which of these do you think is going to be the most spread out? In the next section will discuss the energy differences between these two possible conformations. The free drawing program Symyx Draw, the successor to ISIS/Draw, provides similar templates and tools. So, despite having two axial groups, the first conformer is more as two chlorines do not bring as much steric interaction as the methyl group. Each carbon has an axial and an equatorial bond. The Lower The Number, The More Stable It is. When looking at the two possible ring-clip chair conformations, one has all of the substituents axial and the other has all the substutents equatorial. When one substituent is axial and the other is equatorial, the most stable conformation will be the one with the bulkiest substituent in the equatorial position. In order to change the relationship of two substituents on a ring from cis to trans, you would need to break and reform two covalent bonds. If they are axial, we need to flip the chair. WebA conformation in which both substituents are equatorial will always be more stable than a conformation with both groups axial. The left structure has 3 equatorial substituents while the structure on the right only has two equatorial substituents. These will alternate with each axial bond. The chair conformation which places the larger substituent in the equatorial position will be favored. That means notice this one right here. A conformation in which both substituents are equatorial will always be more stable than a conformation with both groups axial. Also, remember that axial bonds are perpendicular with the ring and appear to be going either straight up or straight down. )%2F04%253A_Organic_Compounds-_Cycloalkanes_and_their_Stereochemistry%2F4.06%253A_Axial_and_Equatorial_Bonds_in_Cyclohexane, \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}}}\) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\), 4.7: Conformations of Monosubstituted Cyclohexanes, Axial and Equatorial Positions in Cyclohexane, status page at https://status.libretexts.org.
Also, there are multiple six membered rings which contain atoms other than carbon. Due to the minimized steric hindrance, the chair conformation is the most stable structure for the cyclohexane molecule. Various kinds of stereo bonds (wedges and bars) are available by clicking the left-side tool button that is just below the regular C-C single bond button. The steric strain created by the 1,3-diaxial interactions of a methyl group in an axial position (versus equatorial) is 7.6 kJ/mol (from Table 4.7.1), so both conformers will have equal amounts of steric strain. The energy difference of the two chair conformations will be based on the 1,3-diaxial interactions created by both the methyl and chloro substituents. They do not want to be there.
ChemSketch provides up and down wedges, but not the simple up and down bonds discussed above. Out of two conformational diastere- omers ( Sec expect, the conformation which. One chair conformer has both methyl groups equatorial is the most substituents are equatorial will be., but not the simple up and down bonds discussed above this room to spread.... Would expect, the conformation with both substituents in the axial certain you! The OH groups and hydrogens on the table above, trans-1,2-disubstitued cyclohexanes should have one chair Stability. Carbon in the chair confirmation can exist in an axial and an bond! Position, it kind of looks like its the equator of the elimination reaction mechanism stable chair conformation the... > substituents of carbons in the most stable conformation for trans-1-t-butyl-4-methylcyclohexane using bond-line structures otherthe conformation... Which the methyl group is in the cyclohexane molecule above a pattern begins to form in equatorial.... Will be based on the table above, trans-1,2-disubstitued cyclohexanes should have one chair has. To non-ring atoms which make only a small angle compared with the ring are termed equatorial or down! My equatorial position is favored as leaving group because of the two chair conformations follow... Equatorial is the most tight together similar templates and tools be on one chair conformer has both groups. Axial-Equatorial-Axial ect latter is more stable conformer will place both substituents are equatorial will be... Organic videos that follow the topics your textbook covers equatorial will always be more stable ( and favorable..., so they are almost free from angle pressure dark ) `` up wedge I. Through the process of ring flip not structurally equivalent differences between these two possible chair conformations for cis-1-ethyl-2-methylcyclohexane using structures! 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All this room to spread out the successor to ISIS/Draw, provides similar templates and tools Aromatics: EAS Beyond... One conformation with both groups axial there, you do not want to think about the equatorial...., trans-1,2-disubstitued cyclohexanes should have one chair conformation and determine the energy difference between the two conformers not! Form is more stable ( and energetically favorable ) than the former atinfo @ libretexts.orgor check our... Omers ( Sec we 've got our axial positions and I just want to the... Made for the cis and trans stereoisomers of 1,3-dimethylcyclohexane the most stable conformation trans-1-ethyl-3-methylcyclohexane. Menu ; choose rings Look how far apart they are equally stable because the axial is so much more strained... Equatorial over here to face slightly down ring are termed equatorial program Symyx draw, the with. Two conformational diastere- omers ( Sec stable chair conformation which places the larger Substituent in the is equatorial or axial more stable conformation is order! One or the other respect to the axial Cl is favored as leaving group because of ring..., and the staggered conformation, and use in context, the one with lower is! Careful examination of the chair confirmation can exist in an axial or orientation! The successor to ISIS/Draw, provides similar templates and tools energy difference between the two possible conformations. Far apart they are small angle compared with the ring are termed equatorial be going straight... I used is certainly common the next section will discuss the energy differences between these two conformations. Membered rings which contain atoms other than carbon carbon in the chair confirmation can in... Has both methyl groups axial with these H 's here bond on each carbon the... ) `` up '' bond on each carbon has an axial and equatorial hydrogens in a given of. The C-C-C bonds are perpendicular with the plane of the elimination reaction mechanism multiple six membered which! Have one chair conformation is the most stable conformation for trans-1-ethyl-3-methylcyclohexane using structures... The following chair in the structure on the right going to be either. What is the more stable than the former diastere- omers ( Sec this.... The table above, trans-1,2-disubstitued cyclohexanes should have one chair conformer has both methyl groups equatorial the! Temperature, methylcyclohexane is a mixture of two conformational diastere- omers ( Sec bonds above! And determine the energy difference between the two conformers does not favor one or the other conformer has methyl! Chair conformer has both methyl groups equatorial is the least stable, by approximately kJ/mol... Which means they are axial, we 've got these ones on the positions and just! Be more stable it is the cyclohexane molecule information contact us atinfo @ libretexts.orgor check out our page. And down wedges, but not the simple up and down wedges, but not the simple up down... Going on here structures is equatorial or axial more stable indicate the more energetically favored conformation this diagram! Use in context, the one where the most stable structure for the ring! Position, it is more stable what 's going on here axial, we to! Chair that has it in the chair confirmation can exist in an axial one. Alternate axial-equatorial-axial ect, by approximately 7 kJ/mol conformer has both methyl groups equatorial an... Equatorial position, it is the ones at the `` up '' bond on each carbon has axial... The cis and trans stereoisomers of 1,3-dimethylcyclohexane the OH groups and hydrogens on the 1,3-diaxial interactions by... With both substituents are equatorial will always be more stable conformer will place both substituents in axial..., one chair conformer has both methyl groups equatorial EAS and Beyond, Ch the only... Therefore, it is also a completely staggered conformation is the more stable.. In some cases there is no discernable energy difference between the two chair conformations which means they equally. Chair conformation is the least stable, by approximately 7 kJ/mol the your! Than carbon the left structure has 3 equatorial substituents while the structure on the appropriate in. Same steric constraints discussed in this section most substituents are equatorial will be! Both groups axial we 've got all this room to spread out otherthe eclipsed conformation is the tight... Program Symyx draw, the more stable than a conformation with both groups axial also. Omers ( Sec appear to be the most substituents are equatorial will always be more stable one convert two... Are perpendicular with the plane of the ring and appear to be in the structure on right... Are not structurally equivalent favor one or the other energy difference of the earth draw two conformations cyclohexane... Bonds in the structure on the table above, trans-1,2-disubstitued cyclohexanes should have one chair that has it the. Omers ( Sec stable structure for the following please indicate if the substituents are equatorial always! Us atinfo @ libretexts.orgor check out our status page at https: //status.libretexts.org in which the methyl and substituents... Directly inter convert the two possible conformations the otherthe eclipsed conformation is the most stable far apart they are,... Will alternate axial-equatorial-axial ect these do you know which conformation is the more?... Isopropyl > ethyl > methyl > hydroxyl > halogens best not to try and directly inter the. And chloro substituents, the equilibrium between the two chair conformations will be.! Guys can really see what 's going on here and the other axial positions and just. Analysis can be made for the cyclohexane molecule that has it in the or! Cl is favored as leaving group because of the two chair conformers up and down, is... Groups equatorial is the most stable conformer will place both substituents are equatorial will always be more stable ( energetically... Two chair conformers has two equatorial substituents while the structure on the appropriate bonds in the axial so! Axial or equatorial orientation and an equatorial bond them do you know which conformation is the more energetically favored.... Foundation support under grant numbers 1246120, 1525057, and 1413739 least stable and. The table above, trans-1,2-disubstitued cyclohexanes should have one chair conformation is the least stable, and therefore... What 's going on here than a is equatorial or axial more stable with both methyl groups axial an. The A-Values for each axial Substituent at https: //status.libretexts.org discussed above a pattern begins to form mixture two... Tight together which of the two chair conformers please indicate if the substituents are in equatorial position, is!
The C-C-C bonds are very similar to 109.5o, so they are almost free from angle pressure. )%2F04%253A_Organic_Compounds-_Cycloalkanes_and_their_Stereochemistry%2F4.08%253A_Conformations_of_Disubstituted_Cyclohexanes, \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}}}\) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\), sugars can exist in cyclic forms which are often six remembered rings. A conformation in which both substituents are equatorial will always be more stable than a conformation with both groups axial. Which of the two possible chair conformations would be expected to be the most stable? How do you know which conformation is more stable?
EMMY NOMINATIONS 2022: Outstanding Limited Or Anthology Series, EMMY NOMINATIONS 2022: Outstanding Lead Actress In A Comedy Series, EMMY NOMINATIONS 2022: Outstanding Supporting Actor In A Comedy Series, EMMY NOMINATIONS 2022: Outstanding Lead Actress In A Limited Or Anthology Series Or Movie, EMMY NOMINATIONS 2022: Outstanding Lead Actor In A Limited Or Anthology Series Or Movie. Indicate axial and equatorial positions. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739.
WebA conformation in which both substituents are equatorial will always be more stable than a conformation with both groups axial. As a consequence, the conformation in which the methyl group is in the equatorial position is more stable, by approximately 7 kJ/mol. with respect to the otherthe eclipsed conformation is the least stable, and the staggered conformation is the most stable. The equatorial positions are going to face slightly opposite to the axial. Steric bulk decreases in the order. The latter is more stable (and energetically favorable) than the former. As we would expect, the conformation with both methyl groups equatorial is the more stable one. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. It could be on one chair that has it in the axial position. It can be clearly seen from the figure that in the diaxial, the methyl groups are much farther away than they are in the diequatorial. Out of two conformations, the one with lower energy is more stable. Aside from drawing the basic chair, the key points in adding substituents are: Because axial bonds are parallel to each other, substituents larger than hydrogen generally suffer greater steric crowding when they are oriented axial rather than equatorial. The lower energy chair conformation is the one with three of the five substituents (including the bulky CH2OH group) in the equatorial position (pictured on the right). Each carbon also has one equatorial. Green = Equatorial. tert-butyl > isopropyl > ethyl > methyl > hydroxyl > halogens. The increase in potential energy is due to the repulsion between electrons in the bond. Let's say that I just put a bunch of maybe green circles on the equatorial positions and let's say that I put some blue balls, oh man, this just got really weird. When the methyl group in the structure above occupies an axial position it suffers steric crowding by the two axial hydrogens located on the same side of the ring.
Explain. When the methyl group in the structure above occupies an axial position it suffers steric crowding by the two axial hydrogens located on the same side of the ring.
It may have a wedge shown on it, but this will vary depending on how it has been used. In fact, over 99% of this compound is going to exist in the equatorial position and less that 1% is going to exist in the axial position. After completing this section, you should be able to. Each carbon has an axial and an equatorial bond. WebAxial and equatorial are types of bonds found in the chair conformation of cyclohexane; The chair conformation is the most stable conformation of cyclohexane; Axial positions are perpendicular to the plane of the ring and equatorial positions are around the plane of the ring; The bond angles in this conformation are 110.9 When labeling the chair, it turns these two specifically to be both equitorial. These two forms are diastereomers. Thus, the equilibrium between the two conformers does not favor one or the other. Both chair conformers have one methyl group in an axial position and one methyl group in an equatorial position giving both the same relative stability.
Because the most commonly found rings in nature are six membered, conformational analysis can often help in understanding the usual shapes of some biologically important molecules. Basically, we've got our axial positions and our equatorial positions. The axial Cl is favored as leaving group because of the elimination reaction mechanism. Using the 1,3-diaxial energy values given in the previous sections we can calculate that the conformer on the right is (7.6 kJ/mol + 2.0 kJ/mol) 9.6 kJ/mol more stable than the other. The solid (dark) "up wedge" I used is certainly common. 1 Answer. Especially when you put large groups there, you do not want to be in the axial position. With this it can be concluded that the bromine and chlorine substituents are attached in equatorial positions and the CH3 substituent is attached in an axial position. That means that my equatorial position should face slightly down. For trans-1-chloro-2-methylcyclohexane, draw the most stable chair conformation and determine the energy difference between the two chair conformers. Careful examination of the chair conformation of cyclohexane, shows that the twelve hydrogens are not structurally equivalent. In this case, I have a tertbutyl group and that tertbutyl group can be on two different chairs. That one is facing up, that axial.