How to judge the cis trans isomerism of substituted cyclohexane and why1,4

First of all, it depends on what your substituent is, if it is two large groups such as tert-butyl groups, etc., they should occupy an approximate flat bond (E bond) as much as possible, that is to say, two substituents replace the hydrogen atoms on 1,6 two pairs, but because it is a large substituent, the intramolecular tension is too large, forcing the conformational distortion of cyclohexane to form a torsion ship type, so that a cis substitute of a twist ship type will be formed. In general, if it is a small group, such as cis 1,2 dimethylcyclogong compensatory, then the two methyl groups will be more inclined to be on the 1-position A bond (vertical bond) and the 2-position E bond or the 1-position E bond and the 2-position A bond, the energy of the two is not much different, and it is relatively low, so it is more stable.

This kind of question is recommended for your reference.

Basic Organic Chemistry.

This book, this is undergraduate content, and it is still relatively difficult.

The vertical is the A bond, the horizontal is the E bond, because the E bond is more stable, so when judging 2 substitution, first put the large substituent on the E bond, and then look at the substitution position and cis or trans. In short, 1,2 replaces cis EA, trans EE; 1,3 replaces cis EE, trans EA; 1, 4 substitution, cis EA, trans EE. As for why transdimethylcyclohexane can't have AE conformation, it is because the title requires trans, and if it is AE, it is cis.

Shun refers to the isolateral of the two substituents in the ring plane, and the opposite refers to the heterogeneity of the two substituents in the ring plane.

Your second question is "why 1,4-disubstituted cyclohexane."

Named it 'cis-reverse'"?

This is because the molecule of 1,4-disubstituted cyclohexane has a symmetry plane (regardless of what the substituent is, unless the substituent is also chiral and therefore not chiral). In this way, 1,4-disubstituted cyclohexane has only two isomers, and it is enough to label it with cis, which is simple and unambiguous.

In the case of 3-disubstituted cyclohexane, the molecule is usually chiral (unless there are two identical substituents on the same side of the ring). In this way, normally (specifically, except in the case of two substituents with the same substituent) they all have four isomers (three when two substituents are the same), and they cannot be labeled with cis-trans, and the RS naming system is used.

Cyclohexane. The one on the same side is called cis, and the one on the other side is called trans.

Cyclohexane is hexagonal in the plane.

, its stereoisomerism is cis and trans on or below the plane. The a,e keys are in opposite directions.

In fact, whether it's a key or an E key, there are three interleaved up and down. That is, if a key is up, then the E key must be slightly downwards, not upwards.

In this case, it is marked, which is the same as in the case of "cyclohexane is pulled into the hexagonal plane".

The easiest way to do this is to putCyclohexane. Think of it as a flat structure. However, after the lift, you can see whether the two methyl groups are on one side of the plane or on both sides. One side is cis, and the two sides are trans.

Chinese name: cyclopentane.

English name: cyclopentane

Molecular structure: C atoms form bonds with sp3 hybrid orbitals.

Molecular formula: C5H10

Molecular weight: physicochemical properties. Appearance and properties: colorless transparent liquid, with benzene-like odor. Melting point ( ) Boiling point ( ) Relative density (water = 1): Relative vapor density (air = 1): Saturation vapor pressure.

kpa): heat of combustion (kj mol): critical temperature ( ) critical pressure (mpa):

Octanol Water partition coefficient logarithmic: 7 (calculated) flash point ( ) Ignition temperature with zetan-25 ( ) 361 ** upper % (v v) :* * lower limit % (v v):

Solubility: insoluble in water, soluble in alcohol, ether, benzene, carbon tetrachloride.

Most organic solvents such as acetone.

Main uses: Cyclopentane as a rigid polyurethane foam.

A new type of blowing agent used to replace the ozone layer on the atmosphere.

Chlorofluorocarbons (CFCs), which have a destructive effect, have been widely used in the production of fluorine-free refrigerators, freezer industries, cold storage, pipeline insulation and other fields. With Montreal.

As the deadline for banning ODS stipulated in the convention approaches, CFCS and HCFCS products will soon be banned, and cyclopentane will surely become the protagonist in the field of polyurethane blowing agents.

Cyclohexane. The molecular formula is: C H, and its trichlorogenate has a total of six isomers.

If you distinguish the optical isomerism, there are a total of nineteen celery rocks:

There are two chlorine in the same carbon atom.

Above: 1,2-Trichloroqingyun cyclohexane (it has two optical isomers) <> 1,3-Trichlorocyclohexane (it has two optical isomers) <> 1,4-Trichlorocyclohexane (no optical isomer).

b. None of the three chlorines are on the same carbon atom: 2,3-trichlorocyclohexane (it has four optical isomers), 2,4-trichlorocyclohexane (he has eight optical isomers) <> 3,5-trichlorocyclohexane (it has two optical isomers) <>

Hexane has 5 isomers, and the specific structure is as follows:

1. N-hexane with 6 carbons on the main chain. The structural formula is shown in the figure below:

2. 2-methylpentane with 5 carbons on the main chain. The structural formula is shown in the figure below:

3. 3-methylpentane with 5 carbons on the main chain. The structural formula is shown in the figure below:

4. There are 4 carbons on the main chain of 2,3-dimethylpyrinobutane. The structural formula is shown in the figure below:

5. There are 4 carbon 2,2-dimethylbutane on the main chain. The structural formula is shown in the figure below:

Cyclohexane. The one on the same side is called cis, and the one on the other side is called trans.

Cyclohexane is hexagonal in the plane.

, its stereoisomerism is cis and trans on or below the plane. The a,e keys are in opposite directions.

In fact, whether it's a key or an E key, there are three interleaved up and down. That is, if a key is up, then the E key must be slightly down, not up.

In this case, it is marked, which is the same as in the case of "cyclohexane is pulled into the hexagonal plane".

The one on the same side is called cis, and the one on the other side is called trans.

According to the regulations:

C-trans nomenclature is used for substances that contain the same or similar groups around the carbon-carbon double bond, with the same (similar) group being cis on the same side and trans on the opposite side.

ZE naming is a generalization of cis-negative naming, comparing the size of the group, the two larger groups are on the same side is cis, and the opposite side is trans.

Generally speaking, cis-trans isomerism is a kind of stereo-isomerism, is an isomerization phenomenon, there are two kinds of nomenclature for cis-trans isomers, namely cis-trans nomenclature and ze nomenclature, the former is a relatively primitive and simple nomenclature, the latter is an improved and perfect nomenclature, although the two nomenclature are related but two independent methods, so there is no correspondence.

There is no cis-trans isomerism in cyclohexane, only boat and chair...

If it also has substituents on it, it is possible to have cis-trans isomerism.

Although the E key in the chair concept is a flat button, it is also a bit oblique and the opposite of the A key (A up and E down). As for the forward and negative, it is necessary to project it into a plane to see that two identical groups are in the same direction, and the reverse is reversed. 1,2-Dimethylcyclohexane, for example.

The word count is small, but it is certainly high-quality, hhh).

The same atom or cluster of atoms on the same side of the c=c bond is called cis, and the one on the opposite side is called trans.

Because carbon-carbon double bonds are irreversible, they form isomers with the same molecular composition but different spatial structures (A and B are different atoms or clusters), a phenomenon called cis-trans isomerism.

The conformation of cyclohexane is most likely to be a chair conformation, but for convenience, cyclohexane is usually studied as a planar six-membered ring, and the answer obtained is the same as when studied as a chair conformation.

If both substitutions are above or below the plane, it is cis, and if one is above the plane and one is below the plane, it is trans.

In the cis configuration, the methyl group and tert-butyl group are on the same side of the six-membered ring, which should be the upper left side. In the trans configuration, the methyl group and tert-butyl group are on either side of the six-membered ring, corresponding to the tert-butyl group facing the upper left and the methyl group facing the lower right.

Considering the rotation of the n-butane C2-C3 bond, the two methyl groups are the fattest groups, so the two methyl groups should be kept as far away as possible to reduce the repulsion, cis-1-methyl-4-tert-butylcyclohexane, the fatter tert-butyl group should be on the flat bond (E bond), and the methyl group can only be on the upright bond (A bond).

In the cis configuration, the methyl group and tert-butyl group are on the same side of the six-membered ring, which should be the upper left side according to the diagram.

In the trans configuration, the methyl group and tert-butyl group are on either side of the six-membered ring. In the corresponding diagram, the tert-butyl group is facing the upper left and the methyl group is facing the lower right.

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