Which conformation of cyclohexane is chiral

Law Change. Animation and Design Change. Quick Link BDes M. Media, Mass Communication and Journalism Change. Quick Links B. Com M. Go To Your Study Dashboard. Home Engineering Can someone explain Which one of the following conformations of cyclohexane is chiral? Post Answer. S subam. As we learnt , Optically active compound - Those compounds having capacity to rotate plane polarised light is called optically active compound.

In the cases of 1,2-, 1,3- and 1,4-disubstituted compounds the analysis is a bit more complex. It is always possible to have both groups equatorial, but whether this requires a cis-relationship or a trans-relationship depends on the relative location of the substituents. As we count around the ring from carbon 1 to 6, the uppermost bond on each carbon changes its orientation from equatorial or axial to axial or equatorial and back.

It is important to remember that the bonds on a given side of a chair ring-conformation always alternate in this fashion. Therefore, it should be clear that for cis-1,2-disubstitution, one of the substituents must be equatorial and the other axial; in the trans-isomer both may be equatorial.

Finally, 1,4-disubstitution reverts to the 1,2-pattern. The conformations of some substituted cyclohexanes may be examined as interactive models by. For additional information about six-membered ring conformations Click Here.

Practice Problems. These four problems concern the recognition of different conformations of a given constitutional structure. Axial and equatorial relationships of cyclohexane substituents are also examined. Return to Table of Contents. This page is the property of William Reusch. Comments, questions and errors should be sent to whreusch msu. These pages are provided to the IOCD to assist in capacity building in chemical education.

Stereoisomers Part II. As chemists studied organic compounds isolated from plants and animals, a new and subtle type of configurational stereoisomerism was discovered.

For example, lactic acid a C 3 H 6 O 3 carboxylic acid was found in sour milk as well as in the blood and muscle fluids of animals. The physical properties of this simple compound were identical, regardless of the source m. Another natural product, the fragrant C 10 H 14 O ketone carvone, was isolated from both spearmint and caraway.

Again, all the physical properties of carvone from these two sources seemed to be identical b. Other examples of this kind were encountered, and suspicions of a subtle kind of stereoisomerism were confirmed by the different interaction these compounds displayed with plane polarized light. We now know that this configurational stereoisomerism is due to different right and left-handed forms that certain structures may adopt, in much the same way that a screw may have right or left-handed threads but the same overall size and shape.

Isomeric pairs of this kind are termed enantiomers from the Greek enantion meaning opposite. All objects may be classified with respect to a property we call chirality from the Greek cheir meaning hand. A chiral object is not identical in all respects i. An achiral object is identical with superimposable on its mirror image. Chiral objects have a "handedness", for example, golf clubs, scissors, shoes and a corkscrew.

Thus, one can buy right or left-handed golf clubs and scissors. Likewise, gloves and shoes come in pairs, a right and a left. Achiral objects do not have a handedness, for example, a baseball bat no writing or logos on it , a plain round ball, a pencil, a T-shirt and a nail. The chirality of an object is related to its symmetry, and to this end it is useful to recognize certain symmetry elements that may be associated with a given object. A symmetry element is a plane, a line or a point in or through an object, about which a rotation or reflection leaves the object in an orientation indistinguishable from the original.

Some examples of symmetry elements are shown below. The face playing card provides an example of a center or point of symmetry. Four random lines of this kind are shown in green. An example of a molecular configuration having a point of symmetry is E -1,2-dichloroethene. Another way of describing a point of symmetry is to note that any point in the object is reproduced by reflection through the center onto the other side.

In these two cases the point of symmetry is colored magenta. A plane of symmetry divides the object in such a way that the points on one side of the plane are equivalent to the points on the other side by reflection through the plane.

In addition to the point of symmetry noted earlier, E -1,2-dichloroethene also has a plane of symmetry the plane defined by the six atoms , and a C 2 axis, passing through the center perpendicular to the plane. The existence of a reflective symmetry element a point or plane of symmetry is sufficient to assure that the object having that element is achiral.

Chiral objects, therefore, do not have any reflective symmetry elements, but may have rotational symmetry axes, since these elements do not require reflection to operate. In addition to the chiral vs achiral distinction, there are two other terms often used to refer to the symmetry of an object. These are: i Dissymmetry : The absence of reflective symmetry elements. All dissymmetric objects are chiral. All asymmetric objects are chiral. Models of some additional three-dimensional examples are provided on the interactive symmetry page.

The symmetry elements of a structure provide insight concerning the structural equivalence or nonequivalence of similar component atoms or groups Examples of this symmetry analysis may be viewed by Clicking Here. To view this site Click Here. A consideration of the chirality of molecular configurations explains the curious stereoisomerism observed for lactic acid, carvone and a multitude of other organic compounds.

Tetravalent carbons have a tetrahedral configuration. If all four substituent groups are the same, as in methane or tetrachloromethane, the configuration is that of a highly symmetric "regular tetrahedron". If one of the carbon substituents is different from the other three, the degree of symmetry is lowered to a C 3 axis and three planes of symmetry, but the configuration remains achiral. The tetrahedral configuration in such compounds is no longer regular, since bond lengths and bond angles change as the bonded atoms or groups change.

Further substitution may reduce the symmetry even more, but as long as two of the four substituents are the same there is always a plane of symmetry that bisects the angle linking those substituents, so these configurations are also achiral. A carbon atom that is bonded to four different atoms or groups loses all symmetry, and is often referred to as an asymmetric carbon.

The configuration of such a molecular unit is chiral, and the structure may exist in either a right-handed configuration or a left-handed configuration one the mirror image of the other. This type of configurational stereoisomerism is termed enantiomorphism , and the non-identical, mirror-image pair of stereoisomers that result are called enantiomers.

The mirror image relationship can be seen by comparing the " ring flip " conformation of the Chair Projection on the right to the current conformation of the Chair Projection on the left. For instruction on how to perform a " ring flip ," click here. Therefore, these molecules are enantiomers. A chair conformation is one of many conformations of a cyclohexane ring and it is most stable. It has equatorial and axial bonds.

The equatorial bonds e are perpendicular to the axis of the ring, while axial bonds a are parallel to the axis of the ring. Cyclopropane is necessarily planar flat , with the carbon atoms at the corners of an equilateral triangle. Planar : Said of a molecule when all of its atoms lie in the same plane. Verify this by building benzene with your molecular model kit. Bond-line structure. Molecular model kit. Despite its bond-line structure drawing, in its lowest energy conformation cyclohexane is a chair, and not planar.

Carl Wilhelm Scheele made an important contribution to stereochemistry when studying the barrels and corks during grape juice fermentation. He discovered racemic acid in which had the identical structure same chemical formula of tartaric acid. The reason is that when substituents are in the axial position, there tends to be more unfavorable interactions with other axial atoms on the same side. When substituents are in the equatorial position, they are farther away from each other.

This increases the stability of the conformation. The chair conformer of the cis 1,2-dichloro isomer is chiral. It exists as a mixture of enantiomeric conformations, which interconvert so rapidly they cannot be resolved ie. Since the cis isomer has two centers of chirality asymmetric carbons and is optically inactive, it is a meso-compound. It is one of the isomers of heptane. The molecule is chiral , and is one of the two isomers of heptane to have this property.

The enantiomers are R - 3 - methylhexane and S - 3 - methylhexane. Epinephrine contains a chiral center in its structure. When epinephrine is used as a drug, the routine organic synthesis results in a racemic mixture. Which conformation of cyclohexane is chiral?

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