Chemistry: Stereochemistry and Alkenes

The specific arrangement of atoms in a molecule, particularly around a double bond, which determines its shape and properties.

A type of isomerism where molecules have the same atoms and bonds but differ in their spatial arrangement, making them non-superimposable.

A carbon atom that is bonded to four different groups, resulting in the molecule having a non-superimposable mirror image.

A 1:1 mixture of enantiomers, which are mirror images of each other, resulting in no optical activity.

Mirror images of molecules that cannot be superimposed, resulting in different interactions with polarized light.

Stereoisomers that are not mirror images, and therefore have different physical and chemical properties.

The ability of a molecule to rotate the plane of polarized light. Enantiomers have opposite optical activities and therefore rotate the plane of polarized light in opposite directions.

The study of the three-dimensional arrangement of atoms in molecules and how this arrangement affects their chemical and biological properties.

A carbon atom bonded to four different groups, resulting in a molecule with a non-superimposable mirror image.

The process of assigning priorities to atoms directly bonded to a chiral center based on their atomic number.

The spatial arrangement of atoms in a molecule, leading to different properties.

A stereoisomer that is a non-superimposable mirror image of another molecule.

A 1:1 mixture of two enantiomers, resulting in no optical activity.

The ability of a molecule to rotate the plane of polarized light. Enantiomers rotate it in opposite directions.

A system for classifying enantiomers based on the arrangement of their four priority groups.

The active enantiomer of a drug, responsible for its desired therapeutic effect.

A molecule that is superimposable on its mirror image.

A set of rules used to assign priorities to atoms or groups attached to a chiral carbon.

The configuration of a chiral carbon assigned as R if the priority order of the four groups is clockwise.

The configuration of a chiral carbon assigned as S if the priority order of the four groups is counterclockwise.

A molecule that rotates plane-polarized light to the right (clockwise).

A molecule that rotates plane-polarized light to the left (counterclockwise).

A molecule that contains chiral carbon but is not optically active.

A type of stereoisomers that are not mirror images but have the same molecular formula and connectivity.

A molecule that can exist in two or more stereoisomeric forms.

A molecule with the same molecular formula but different structural formula.

If the lowest priority group (atom with the lowest atomic number) is located in the plane of the molecule, you cannot assign chirality confidently.

Rotating the molecule to place the lowest priority group either at the back or front of the molecule makes assigning chirality easier and generally preferred.

Enantiomers, which are mirror images of each other, rotate plane-polarized light (PPL) in opposite directions but by the same amount.

Clockwise rotation of plane-polarized light is called dextrorotatory and is denoted by a plus (+) sign. Anticlockwise rotation is called levorotatory and denoted by a minus (-) sign.

The specific rotation (+) or (-) does not tell you the absolute configuration (R or S) of the molecule.

The three-point model explains differences in the interactions between enantiomers and other chiral molecules, like receptors and enzymes.

Receptors and enzymes are also chiral because they are made up of amino acids, which are chiral.

Enantiomers can interact differently with other chiral molecules due to their distinct three-dimensional structure.

A nitrogen atom can be chiral if it is bonded to four different groups. However, if the lone pair on the nitrogen can be deprotonated or protonated, it can undergo inversion, resulting in two non-superimposable mirror images of the molecule. This means that the nitrogen no longer fits the definition of a chiral center.

If a nitrogen atom can participate in resonance by donating its lone pair to an adjacent group, it will adopt a partial double bond character. This results in a planar geometry (sp2 hybridization) for the nitrogen, which prevents it from being a chiral center because it does not have four distinct groups attached to it.

An enantiomer is a stereoisomer that is non-superimposable on its mirror image. This means that the two molecules have identical chemical and physical properties except for their interaction with plane-polarized light (PPL).

Enantiomers rotate the plane of polarized light (PPL) by equal amounts but in opposite directions. This is because they interact differently with the electric field of the polarized light.

The inactive enantiomer of a drug can have undesirable effects, ranging from no effect to harmful side effects. This is because the inactive enantiomer can interact with different receptors in the body, leading to unintended consequences.

The direction of rotation of plane-polarized light (PPL) by a molecule is denoted by (+) for dextrorotatory (clockwise rotation) and (-) for levorotatory (counterclockwise rotation). This is independent of the R/S configuration assigned to the chiral center.

Many pharmaceuticals contain one or more chiral centers, which are carbon atoms bonded to four different groups. These chiral centers give rise to enantiomers, which are stereoisomers with different spatial arrangements.

The (S)-enantiomer of Vigabatrin is the active form of the drug, inhibiting GABA transaminase and increasing GABA levels in the brain, leading to reduced seizure activity. The (R)-enantiomer has no known adverse effects.

The (R)-enantiomer of Fluoxetine is rapidly eliminated, while the (S)-enantiomer is the pharmacologically active form due to its higher concentration in the body.

Both enantiomers of Warfarin are active in inhibiting Vitamin K epoxide reductase (VKORC1), but the (S)-form is approximately 4 times more potent than the (R)-form in practice.

While some enantiomers exhibit different activities, it's important to note that not every pair of enantiomers does. For example, the (R)-enantiomer of Vigabatrin has no known adverse effects.

It's crucial to distinguish between undesirable activity in one enantiomer and no adverse activity in the other. For example, the (R)-enantiomer of a drug might be inactive, not having any adverse effects.

The active enantiomer binds correctly to the receptor to trigger the desired response, while the inactive enantiomer cannot bind correctly, failing to initiate a response.

Amines, molecules containing a nitrogen bonded to a carbon atom and at least one hydrogen atom, are rarely chiral because the nitrogen atom often binds to four different groups, making it a potential chiral center. However, the lone pair of electrons on nitrogen acts as a fourth group, rendering the nitrogen non-chiral.

Though both enantiomers of a racemic mixture are present, the mixture exhibits no optical activity due to the equal and opposite rotation of polarized light by the enantiomers.

The (S)-enantiomer of a drug is typically the pharmacologically active form, displaying the desired therapeutic effect. However, it is important to note that sometimes both enantiomers or even the less active enantiomer can provide the desired effect. For example, in Warfarin, the (S)-form is more potent.

The concept of chirality refers to how the arrangement of groups attached to a carbon atom in a molecule can create non-superimposable mirror images, called enantiomers. This leads to different interactions with other chiral molecules, such as receptors. Enantiomers can exhibit different pharmacological activities, explaining why certain drugs work while their mirror image may need to be removed or optimized. The R/S system (Rectus-Sinister) classifies the arrangement of groups around a chiral carbon atom.