Cis-trans isomerism, also known as geometric isomerism or configurational isomerism, is a term used in chemistry that concerns the spatial arrangement of atoms within molecules. (definitions.net)
Chirality of molecules may originate from configurational or conformational effects of structures. (tu-darmstadt.de)
This differentiation of configurational and conformational stereoisomers is not allways unambiguous, but generally conformational isomers may interconvert in each other through rotations about C-C single bonds only (this will not interconvert configurational isomers). (tu-darmstadt.de)
Rotational isomerism and thermodynamic functions of 2-methylbutane and 2,3-dimethylbutane. (nist.gov)
Geometric1
Cis-trans isomerism Also referred to as geometric isomers, these compounds have different configurations due to the inflexible structure of the molecule. (wikipedia.org)
Isomers1
Chiral molecules related to each other as mutual mirror images may be separated into two enantiomers ( reflection isomers , mirror images ) with identical chemical (stability and reactivity in achiral environments) and physical (scalar) properties (melting and boiling point, spectroscopic data, etc.), except for their specific optical rotation (the optical activity of enantiomers is of equal absolute magnitude, but of opposite sign). (tu-darmstadt.de)
Ring structures1
In general, cis-trans stereoisomers contain double bonds that do not rotate, or they may contain ring structures, where the rotation of bonds is restricted or prevented. (definitions.net)
Trans6
Two requirements must be met for a molecule to present cis-trans isomerism: 1. (wikipedia.org)
Cis-trans notation does not always correspond to E-Z isomerism, which is an absolute stereochemical description. (definitions.net)
Proline (Pro) is an outstanding amino acid in various biochemical and physicochemical perspectives, especially when considering the cis - trans isomerism of the peptidyl-Pro amide bond. (beilstein-journals.org)
In particular, Pro residues are often found in the s - cis peptidyl-Pro conformation, due to the low energy difference between the s - trans and the s - cis conformational states (ca. 3-4 kJ/mol) [1,2] . (beilstein-journals.org)
Below examples are given, in which chirality results from conformational effects, whereas chemical formulas at first sight suggest planar conformations of molecules (see 'Helical Chirality' below). (tu-darmstadt.de)
Because the pi bond has a bond energy of roughly 60 kcal/mole, this resistance to rotation stabilizes the planar configuration of this functional group. (libguides.com)
Most accurately, all molecules which have a n -fold alternating axis of symmetry (equal to an improper rotation axis or a rotary-reflection axis , symmetry element S n ) are achiral (and thus superimposable with their mirror images). (tu-darmstadt.de)
neither operation alone (rotation or reflection) is a valid symmetry operation for these molecules, but only the combination of both. (tu-darmstadt.de)
Optical1
This property, the only physical property in which the two types of tartrate salts differed, is due to optical isomerism. (wikipedia.org)
Data1
19F NMR data were used to investigate conformational isomerism in the context of the observed bands is demonstrated in Fig. (irkutsk.ru)
Internal1
Special care is taken to correctly treat the internal rotations to predict accurate values of the preexponential factor. (ugent.be)
Groups2
Anisotropic rotation of amino groups in canonical nucleotide bases. (org.ua)
Rotation of the end groups of a double bond relative to each other destroys the p-orbital overlap that creates the pi orbital or bond. (libguides.com)
Molecules5
However, the amount of rotation actually measured is dependent on the concentration of molecules in the light beam, the pathlength, and the wavelength of the light used. (pharmacy180.com)
Larger molecules often exist in multiple stable geometries ( conformational isomerism ) that are close in energy on the potential energy surface . (wikipedia.org)
X @ C ⋯ Y ₪ ic Y @ C ⋯ X , ( ₪ is the isomerism relation) as an isomerism in the three-component system of molecules X , Y , and a cage C, in which one of the molecules is located inside and the other outside the cage. (mdpi.com)
A major starting point for the design of AMMs is to exploit the existing modes of motion in molecules, such as rotation about single bonds or cis-trans isomerization . (reelpotassiu1.sbs)
Here you correctly determined the E and Z configurations of molecules with identical functional groups, but could have saved yourself some effort if you had recognized W and Z are identical molecules that are inversions/180° rotations of each other. (stackexchange.com)
Molecule5
Two requirements must be met for a molecule to present cis-trans isomerism: 1. (wikipedia.org)
Rotation within the molecule must be restricted. (wikipedia.org)
If equal amounts of enan-tiomers are present, the solution will not exhibit optical activity, because for each molecule that rotates light in one direction there will be another molecule that rotates light in the opposite direction and the net rotation is zero. (pharmacy180.com)
The overall (external) quantum mechanical motions translation and rotation hardly change the geometry of the molecule. (wikipedia.org)
Since these features are dependent on the three-dimensional chemical structure of a molecule, simple structural modifications can affect its conformational stability and, consequently, the corresponding physicochemical/biological property of interest. (beilstein-journals.org)
Carbonyl group2
The carbonyl group also plays a determinant role in the conformational isomerism of ketones and aldehydes [14-17] . (beilstein-journals.org)
a simple bond rotation of an aryl or carbonyl group can invert the sign of the rotation. (imperial.ac.uk)
Molecular3
In addition to translation and rotation, a third type of motion is molecular vibration , which corresponds to internal motions of the atoms such as bond stretching and bond angle variation. (wikipedia.org)
As stated above, rotation hardly influences the molecular geometry. (wikipedia.org)
[4] [5] The advent of conformational analysis, or the study of conformers to analyze complex chemical structures, in the 1950s gave rise to the idea of understanding and controlling relative motion within molecular components for further applications. (reelpotassiu1.sbs)
Compounds2
While the gauche effect, originated from hyperconjugative interactions, does not appear to cause some preferences for the axial conformation of organofluorine heterocycles, more classical effects indeed rule the conformational equilibrium of the compounds. (beilstein-journals.org)
A fluorine substituent in organofluorine compounds affects conformational properties, since it can induce stereoelectronic effects, such as σ C-H to σ* C-F hyperconjugative interactions in case of an antiparallel oriented C-H bond. (beilstein-journals.org)
Structural1
In this work, structural changes in 2-fluorocyclohexanone were theoretically studied with the aim at finding intramolecular interactions that induce the conformational equilibrium towards the axial or equatorial conformer. (beilstein-journals.org)
Enantiomeric2
For example, each enantiomer of an enantiomeric pair produces a rotation of the plane of plane-polarized light to an equal but opposite extent. (pharmacy180.com)
When both enantiomers are present in solution, the observed rotation will reflect the enantiomeric composition of the mixture. (pharmacy180.com)
Optical rotation4
In the article supporting information [1] ), the major diasteromer of 4a deriving from use of the S stereoisomer of the prolinol catalyst is reported as having an optical rotation (ORP) [α] D 25 of -62.4°, p6 or -58.1°, p5), but the stereo-labels are not added there. (imperial.ac.uk)
In Table 1 we can see whether this is still true for the predicted optical rotation of compound 4a , using two different functionals for the calculation (B3LYP and M062X respectively). (imperial.ac.uk)
Clearly the observed optical rotation of -62.4° arises from a suitable combination of different Boltzmann populations of the individual bond rotamers, but to combine these accurately you would need to know the solution populations themselves very accurately and that is quite a challenge. (imperial.ac.uk)
So at this stage, we do not really have totally convincing independent evidence of whether the observed negative optical rotation corresponds to (1 S ,2 R ,3 R )- 4a or to its enantiomer (1 R ,2 S ,3 S ). (imperial.ac.uk)
Bond4
Rotation of the end groups of a double bond relative to each other destroys the p-orbital overlap that creates the pi orbital or bond. (msu.edu)
Because the pi bond has a bond energy of roughly 60 kcal/mole, this resistance to rotation stabilizes the planar configuration of this functional group. (msu.edu)
Additionally, conformational rotation around the formyl bond, C5- N5 bond, and glycosidic bond may occur. (nih.gov)
Why does having identical groups on either side of the pi bond lead to no geometrical isomerism? (stackexchange.com)
Present2
If one enantiomer is present in excess over the other, then the solution will have a net rotation corresponding in sign ( + or − ) to that of the more abundant enantiomer. (pharmacy180.com)
To some extent rotation influences the geometry via Coriolis forces and centrifugal distortion , but this is negligible for the present discussion. (wikipedia.org)
Similar1
The ic isomerism is similar to the endo-exo one, which occurs only if either the interior or exterior of C is empty. (mdpi.com)
Plane-polar2
The enantiomer which produces clockwise rotation of plane-polarized light is designated the positive enantiomer, and the enantiomer which produces counterclockwise rotation of plane-polarized light is designated the negative enantiomer. (pharmacy180.com)
The rotation of plane-polarized light by a pure enantiomer is an inherent prop-erty of that enantiomer. (pharmacy180.com)
To account for these variables, the observed rotation is converted to the specific rotation [ α ], which is defined as the rota-tion observed for a solution of 1 g/mL concentration in a 10-cm-pathlength cell. (pharmacy180.com)
Furthermore a wavelength of 589 nm, the D line of sodium, is normally the standard wavelength for measuring the specific rotation and 25 ◦ C is the standard temperature of the measurement. (pharmacy180.com)