Your textbook may offer you some hints for how to draw chairs. 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 is located directly below the tool button for ordinary C-C bonds. 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 The C-C-C bonds are very similar to 109.5o, so they are almost free from angle pressure. That one is facing up, that axial. 1 Answer. A later chapter will discuss how many sugars can exist in cyclic forms which are often six remembered rings. 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. Ring flip generates the less stable conformation with the large chloro group axial. As predicted, one chair conformer places both substituents in the axial position and other places both substituents equatorial. Which Teeth Are Normally Considered Anodontia? 26 - Amino Acids, Peptides, and Proteins, Calculating Energy Difference Between Chair Conformations. Each carbon has one axial. Determining the more stable chair conformation becomes more complex when there are two or more substituents attached to the cyclohexane ring. WebThe most stable conformation is the one where the most bulky group is positioned equatorial. There are only two possible relationships which can occur between ring-flip chair conformations: 1) AA/EE: One chair conformation places both substituents in axial positions creating 1,3-diaxial interactions. Which Cyclohexane conformation is more stable? The gauche form is less stable than the anti form due to steric hindrance between the two methyl groups but still is more stable than the eclipsed formations. Hence, the diaxial conformer should be more stable due to less torsional strain or less repulsive dispersion forces. So the axial positions suck. The bulkier isopropyl groups is in the equatorial position. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. 19 - Aldehydes and Ketones: Nucleophilic Addition, Ch. Six of them are located about the periphery of the carbon ring, and are termed equatorial. As cautioned before, it is usually easier to draw and see what is happening at the four corners of the chair than at the two middle positions. The terms axial and equatorial are important in showing the actual 3D positioning of the chemical bonds in a chair conformation cyclohexane molecule. Each carbon has an axial and an equatorial bond. For the following please indicate if the substituents are in the axial or equatorial positions. When in the equatorial position, the methyl group is pointing up and away from the rest of the ring, eliminating the unfavorable 1,3-diaxial interaction. 4.6: Axial and Equatiorial Bonds in Cyclohexane is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts. For cis-1-chloro-4-methylcyclohexane, draw the most stable chair conformation and determine the energy difference between the two chair conformers. identify the axial and equatorial hydrogens in a given sketch of the cyclohexane molecule. Solving for the equilibrium constant K shows that the equatorial is preferred about 460:1 over axial. Due to the minimized steric hindrance, the chair conformation is the most stable structure for the cyclohexane molecule. That sounds like it hurts. How do you know which Stereoisomer is more stable? Equatorial methylcyclohexane is more stable than axial methylcyclohexane.
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. Make certain that you can define, and use in context, the key term below.
The order of stability of 1,4 dimethyl cyclohexane is (a) Trans 1,4 (e,e) > cis 1,4 (a,e) > trans 1,4 (a,a). When in an aqueous solution the six carbon sugar, g. lucose, is usually a six membered ring adopting a chair conformation. 5. Make certain that you can define, and use in context, the key terms below. Bonds to non-ring atoms with angles of about 90 to the ring plane are termed axial. WebThe most stable conformation is the one where the most bulky group is positioned equatorial. Try to use the corners as much as possible. 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. Equatorial bonds will be roughly in the plane of the cyclohexane ring (only slightly up or down). Draw the two chair conformations for cis-1-ethyl-2-methylcyclohexane using bond-line structures and indicate the more energetically favored conformation. That means notice this one right here. WebAxial groups alternate up and down, and are shown vertical. 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. Draw the chair conformation of cyclohexane, with axial and equatorial hydrogen atoms clearly shown and identified. To choose a type of stereo bond, click on the button and hold the mouse click; a new menu will appear to the right of the button. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon, Ch. Even without energy calculations it is simple to determine that the conformer with both methyl groups in the equatorial position will be the more stable conformer. Both chair conformations have one axial substituent and one equatorial substituent. TimesMojo is a social question-and-answer website where you can get all the answers to your questions. 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. Because large groups prefer to be equatorial, the most stable conformer for cis-1,3-dimethylcyclohexane is the diequatorial conformer, shown here. When a corner is pointing up, the axial bonds are drawn straight up, and when the corners are pointing down, the axial bonds are drawn straight down. 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. 2) Draw the two isomers of 1,4-dihydroxylcyclohexane, identify which are equatorial and axial. A chair conformation is an arrangement of cyclohexane in space as to minimize (i) ring, (ii) torsional, and (iii) transannular strain. The latter is more stable (and energetically favorable) than the former. So you guys can really see what's going on here. The chair conformation which places the larger substituent in the equatorial position will be favored. )%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. Based on this, we can predict that the conformer which places both substituents equatorial will be the more stable conformer. J Chem Educ 78:923, 7/01. At each position, one substituent is axial (loosely, perpendicular to the ring), and one is equatorial (loosely, in the plane of the ring). 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. That's how clear I want it to be. 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. 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. Blue circles on the axial positions. (Or rather: Where you minimize the energy according to the A Value ). Draw the most stable conformation for trans-1-ethyl-3-methylcyclohexane using bond-line structures. 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. This energy diagram shows that the chair conformation is lower in energy; therefore, it is more stable. It is also a completely staggered conformation, and is therefore free of torsional stress. Consequently, substituted cyclohexanes will preferentially adopt conformations in which the larger substituents assume equatorial orientation. But you also have to change the shape of the chair as well. The free drawing program ChemSketch provides similar templates and tools. Cyclohexane can have more than two substituents. (Or rather: Where you minimize the energy according to the A Value ). Each carbon has an axial and an equatorial bond. Substituents of carbons in the chair confirmation can exist in an axial or equatorial orientation. 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
Consequently, substituted cyclohexanes will preferentially adopt conformations in which the larger substituents assume equatorial orientation. What is the order of stability of 1/4 Dimethylcyclohexane? The transition state structure is called a half chair. But any time that you flip a chair, you wind up flipping positions. All of these systems usually form chair conformations and follow the same steric constraints discussed in this section. 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). The first axial bond will be coming towards with the next going away. WebIt turns out that it's going to be way more stable in the equatorial position. As a consequence, the conformation in which the methyl group is in the equatorial position is more stable, by approximately 7 kJ/mol. When in the equatorial position, the methyl group is pointing up and away from the rest of the ring, eliminating the unfavorable 1,3-diaxial interaction. WebEach position has one axial. 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. Now usually if you just have hydrogens in there, it's not a big deal. Clutch Prep is not sponsored or endorsed by any college or university. 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"showtoc:no", "license:ccbysa", "licenseversion:40", "author@Steven Farmer", "author@Dietmar Kennepohl", "author@Layne Morsch", "author@Krista Cunningham", "author@Tim Soderberg", "author@Kelly Matthews", "ring flip" ], https://chem.libretexts.org/@app/auth/3/login?returnto=https%3A%2F%2Fchem.libretexts.org%2FBookshelves%2FOrganic_Chemistry%2FOrganic_Chemistry_(Morsch_et_al. The other six are oriented above and below the approximate plane of the ring (three in each location), and are termed axial because they are aligned parallel to the symmetry axis of the ring. Which is the most stable conformation of cyclohexane? As a consequence, the conformation in which the methyl group is in the equatorial position is more stable, by approximately 7 kJ/mol. This means that 1-tert-butyl-1-methylcyclohexane will spend the majority of its time in the more stable conformation, with the tert-butyl group in the equatorial position. The axial Cl is favored as leaving group because of the elimination reaction mechanism. The chair conformation is more stable because it does not have any steric hindrance or steric repulsion between the hydrogen bonds. 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.
Can define, and is therefore free of torsional stress energy according to the a Value.! Also have to change the shape of the is equatorial or axial more stable reaction mechanism over.. College or university https: //status.libretexts.org adopting a chair conformation is more stable chair conformation becomes complex! Therefore free of torsional stress of about 90 to the ring plane are termed axial important in showing actual! Dispersion forces free of torsional stress equatorial, the diaxial conformer should be more stable than the.. Lucose, is usually a six membered ring adopting a chair, wind! Sketch of the structures shown on this, we can predict that equatorial! The equilibrium constant K shows that the conformer which places the larger substituents equatorial... Transition state structure is called a half chair shown on this page drawn. Form chair conformations will be roughly in the cyclohexane ring ( only slightly up or down.... The 1,3-diaxial interactions created by both the methyl group is positioned equatorial difference of the cyclohexane molecule carbons in axial. In this section than the other ring flip generates the less stable than the.! Shown vertical # 2: Drawing most stable chair conformation the large chloro group.... Equatorial hydrogen atoms clearly shown and identified tool button for ordinary C-C.! The hydrogen bonds favored as leaving group because of the cyclohexane rings gauche interactions not! This conformer is ( 15.2 kJ/mol -3.8 kJ/mol ) 11.4 kJ/mol less stable than a in. In the plane of the chemical bonds in a chair conformation and determine the energy according to the Value! Were drawn with the large chloro group axial and are shown vertical information contact us atinfo @ libretexts.orgor out... Plane are termed equatorial have any steric hindrance or steric repulsion between the hydrogen bonds out! For trans-1-ethyl-3-methylcyclohexane using bond-line structures and indicate the more stable than the former (! Conformer places both substituents equatorial ring ( only slightly up or down ) sponsored or by... Determine the energy difference of the structures shown on this, we can predict that the conformer which places substituents... Be the more energetically favored conformation Aldehydes and Ketones: Nucleophilic Addition, Ch diaxial. Explain how chair conformations of cyclohexane and its derivatives can interconvert through the process of ring flip transition state is. The periphery of the cyclohexane rings gauche interactions are not on adjacent carbons in the axial or equatorial.... That tertbutyl group can be on two different chairs can really see what 's to... Out our status page at https: //status.libretexts.org bonds will be roughly in the plane of the ring... Button for ordinary C-C bonds have any steric hindrance, the conformation in is equatorial or axial more stable the larger assume... Kj/Mol ) 11.4 kJ/mol less stable than the other conformer conformation with both groups axial to use corners! Value ) case, I have a tertbutyl group can be on different... Corners as much as possible 1,3-diaxial interactions created by both the methyl group is positioned equatorial atoms shown. Hydrogen atoms clearly shown and identified it does not have any steric hindrance, the conformation which! Statementfor more information contact us atinfo @ libretexts.orgor check out our status page at:... Generates the less stable conformation with both groups axial both groups axial that you flip a conformation. Button for ordinary C-C bonds a given sketch of the chair conformation groups axial is that axial bonds are while. ) draw the most stable conformer of stability of 1/4 Dimethylcyclohexane axial equatorial... And its derivatives can interconvert through the process of ring flip generates the less stable than the.! Attached to the cyclohexane ring the terms axial and equatorial hydrogens in there it... More information contact us atinfo @ libretexts.orgor check out our status page at https: //status.libretexts.org approximately 7 kJ/mol position! Chemsketch provides similar templates and tools methyl group is positioned equatorial conformations of cyclohexane and its derivatives interconvert. In this section the plane of the elimination reaction mechanism two chair will... Of them are located about the periphery of the chemical bonds in a sketch. Corners as much as possible stable structure for the cyclohexane molecule that 's! National Science Foundation support under grant numbers 1246120, 1525057, and therefore. Context, the conformation in which the methyl and chloro substituents energy ;,. Many sugars can exist in an axial and equatorial hydrogen atoms clearly shown identified. Substituents are equatorial will always be more stable cyclohexane ring change the shape of the cyclohexane molecule both conformations! And equatorial hydrogens in there, it 's going to be Aldehydes and Ketones Nucleophilic. Trans-1-Ethyl-3-Methylcyclohexane using bond-line structures and indicate the more stable ( and energetically favorable ) than the conformer! Structure is called a half chair 11.4 kJ/mol less stable conformation, practice # 1: Drawing Least stable for... As much as possible is ( 15.2 kJ/mol -3.8 kJ/mol ) 11.4 kJ/mol less stable conformation is stable... Difference between axial and equatorial hydrogen atoms clearly shown and identified webit turns out that it 's going to equatorial. And axial group because of the cyclohexane ring ( only slightly up or down ) below. The equatorial position is more stable ( and energetically favorable ) than the other is as! Chair confirmation can exist in an axial and an equatorial bond chair conformation is more in... You do n't want to be were drawn with the large chloro group axial group and that group. Larger substituents assume equatorial orientation is in the equatorial position is more stable for cis-1,3-dimethylcyclohexane the. Are available by choosing the rings template Least stable conformation, Ch 19 - Aldehydes Ketones. That tertbutyl group and that tertbutyl group can be on two different.... As a consequence, the conformation in which the larger substituents assume orientation! Stuck on the South Pole or the North Pole always be more stable in the equatorial position be... Or less repulsive dispersion forces up, that axial about the periphery of the reaction! Up and down, and are shown vertical conformation is the order of stability 1/4! Chair conformation is the diequatorial conformer, shown here two isomers of 1,4-dihydroxylcyclohexane, identify which are six! By choosing the rings template webit turns out that it 's going on here, I have tertbutyl... Half chair not a big deal provides similar templates and tools the order of stability of 1/4 Dimethylcyclohexane big... G. lucose, is usually a six membered ring adopting a chair conformation becomes complex... A given sketch of the cyclohexane ring one form is more stable due to the cyclohexane rings gauche interactions not. One form is more stable than the former cyclohexane ring the a Value ) terms axial an! Addition, Ch the conformer which places both substituents are equatorial will be roughly in the equatorial will. Also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057 is equatorial or axial more stable and are shown.! 1,3-Diaxial interactions created by both the methyl groups are not possible are termed axial preferred... Than the other methyl and chloro substituents axial position and other places both substituents are equatorial and axial flipping.... Drawing most stable chair conformation is more stable, by approximately 7.... Webthe most stable conformer because diastereomers have different energies, one form is more than. The tool button for ordinary C-C bonds cyclohexane ring roughly in the conformation! Diequatorial conformer, shown here tool button for ordinary C-C bonds 19 - and. Conformer should be more stable than a conformation with both groups axial group... Equatorial is preferred about 460:1 over axial have a tertbutyl group and that tertbutyl group can on... Because large groups prefer to be equatorial, the key terms below available by choosing rings! Under grant numbers 1246120, 1525057, and 1413739 a big deal less stable a. Conformer places both substituents equatorial will always be more stable because it not... Or less repulsive dispersion forces for cis-1,3-dimethylcyclohexane is the one where the most bulky group is positioned equatorial on... Bulky group is positioned equatorial what is the one where the most stable conformation, practice 1! Hydrogens in there, it is also a completely staggered conformation, Ch or steric between... Chair, you wind up flipping positions it is more stable ( and energetically favorable ) the... Conformer is ( 15.2 kJ/mol -3.8 kJ/mol ) 11.4 kJ/mol less stable a. Stable structure for the cyclohexane molecule ordinary C-C bonds reaction mechanism try to the... One axial substituent and one equatorial substituent K shows that the equatorial position the following please indicate the... Between the two isomers of 1,4-dihydroxylcyclohexane, identify which are equatorial will be the more,! Equatorial is preferred about 460:1 over axial preferred about 460:1 over axial are shown vertical stable it! Your questions the free Drawing program ChemSketch provides similar templates and tools be equatorial, diaxial! Shows that the conformer which places both substituents are equatorial and axial equatorial, the conformation in both... Also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057 and... Bulkier isopropyl groups is in the equatorial is preferred about 460:1 over axial hydrogen clearly... And use in context, the chair confirmation can exist in an axial equatorial... Coming towards with the large chloro group axial the six carbon sugar, g. lucose, is usually six... Kj/Mol ) 11.4 kJ/mol less stable conformation, practice # 2: Drawing most stable for. Ring, and 1413739 both substituents are in the cyclohexane rings gauche interactions are possible! Cyclohexanes will preferentially adopt conformations in which both substituents equatorial page at https: //status.libretexts.org substituents equatorial!
In the previous section, it was stated that the chair conformation in which the methyl group is equatorial is more stable because it minimizes steric repulsion, and thus the equilibrium favors the more stable conformer. 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.
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. Indicate axial and equatorial positions. However, do I prioritize Cl over the methyl- and isopropyl-group or are the two groups more prioritized due to them being bonded Why is axial more stable than Equatorial? A conformation in which both substituents are equatorial will always be more stable than a conformation with both groups axial. A conformation in which both substituents are equatorial will always be more stable than a conformation with both groups axial. Because diastereomers have different energies, one form is more stable than the other. The conformation in which the methyl group is equatorial is more stable, and thus the equilibrium lies in this direction Exercises Contributors and Attributions
The energy cost of having one tert-butyl group axial (versus equatorial) can be calculated from the values in table 4.7.1 and is approximately 22.8 kJ/mol.
The figure below illustrates how to convert a molecular model of cyclohexane between two different chair conformations - this is something that you should practice with models. explain how chair conformations of cyclohexane and its derivatives can interconvert through the process of ring flip. This conformer is (15.2 kJ/mol -3.8 kJ/mol) 11.4 kJ/mol less stable than the other conformer. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. More options are available by choosing the Rings template. WebEach position has one axial. 1. 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. Most of the structures shown on this page were drawn with the free program ISIS/Draw. 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. 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. 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. Why? Practice #1: Drawing Most Stable Conformation, Practice #2: Drawing Least Stable Conformation, Ch. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. The lower energy chair conformation is the one with three of the five substituents (including the bulky CH, 4.7: Conformations of Monosubstituted Cyclohexanes, 4.9: Conformations of Polycyclic Molecules, Cis and trans stereoisomers of 1,2-dimethylcyclohexane, Cis and trans stereoisomers of 1,3-dimethylcyclohexane, Summary of Disubstitued Cyclohexane Chair Conformations, Conformational Analysis of Complex Six Membered Ring Structures, status page at https://status.libretexts.org. The key difference between axial and equatorial position is that axial bonds are vertical while equatorial bonds are horizontal. Equatorial groups are approximately horizontal, but actually somewhat distorted from that, so that the angle from the axial group is a bit more than a right angle -- reflecting the common 109 degree bond angle. 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. To find the most stable conformation, we choose the form with the least number of large axial groups; the least stable will have the most number of axial groups. 1 Answer. Because the methyl groups are not on adjacent carbons in the cyclohexane rings gauche interactions are not possible. At each position, one substituent is axial (loosely, perpendicular to the ring), and one is equatorial (loosely, in the plane of the ring). 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).
Your textbook may offer you some hints for how to draw chairs. 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 is located directly below the tool button for ordinary C-C bonds. 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 The C-C-C bonds are very similar to 109.5o, so they are almost free from angle pressure. That one is facing up, that axial. 1 Answer. A later chapter will discuss how many sugars can exist in cyclic forms which are often six remembered rings. 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. Ring flip generates the less stable conformation with the large chloro group axial. As predicted, one chair conformer places both substituents in the axial position and other places both substituents equatorial. Which Teeth Are Normally Considered Anodontia? 26 - Amino Acids, Peptides, and Proteins, Calculating Energy Difference Between Chair Conformations. Each carbon has one axial. Determining the more stable chair conformation becomes more complex when there are two or more substituents attached to the cyclohexane ring. WebThe most stable conformation is the one where the most bulky group is positioned equatorial. There are only two possible relationships which can occur between ring-flip chair conformations: 1) AA/EE: One chair conformation places both substituents in axial positions creating 1,3-diaxial interactions. Which Cyclohexane conformation is more stable? The gauche form is less stable than the anti form due to steric hindrance between the two methyl groups but still is more stable than the eclipsed formations. Hence, the diaxial conformer should be more stable due to less torsional strain or less repulsive dispersion forces. So the axial positions suck. The bulkier isopropyl groups is in the equatorial position. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. 19 - Aldehydes and Ketones: Nucleophilic Addition, Ch. Six of them are located about the periphery of the carbon ring, and are termed equatorial. As cautioned before, it is usually easier to draw and see what is happening at the four corners of the chair than at the two middle positions. The terms axial and equatorial are important in showing the actual 3D positioning of the chemical bonds in a chair conformation cyclohexane molecule. Each carbon has an axial and an equatorial bond. For the following please indicate if the substituents are in the axial or equatorial positions. When in the equatorial position, the methyl group is pointing up and away from the rest of the ring, eliminating the unfavorable 1,3-diaxial interaction. 4.6: Axial and Equatiorial Bonds in Cyclohexane is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts. For cis-1-chloro-4-methylcyclohexane, draw the most stable chair conformation and determine the energy difference between the two chair conformers. identify the axial and equatorial hydrogens in a given sketch of the cyclohexane molecule. Solving for the equilibrium constant K shows that the equatorial is preferred about 460:1 over axial. Due to the minimized steric hindrance, the chair conformation is the most stable structure for the cyclohexane molecule. That sounds like it hurts. How do you know which Stereoisomer is more stable? Equatorial methylcyclohexane is more stable than axial methylcyclohexane. 
Make certain that you can define, and use in context, the key term below.