Stereochemistry Lecture Notes Flashcards

Comprehensive practice flashcards covering the key terminology and definitions of stereochemistry as presented in the lecture by Prof. R. Jagessar.

Stereochemistry

The study of the three dimensional orientation or structure of molecules, depicted by the coordinate dimensions $x$, $y$, and $z$.

Chiral Molecule

A molecule that contains a chiral carbon, often denoted with an asterisk ($*$).

Chiral or Asymmetric Carbon

A carbon atom that is bonded to four different functional groups.

Enantiomers

Stereoisomers whose mirror images and objects are non-superimposable.

Non-superimposable

A property where, if an image is slid over an object, the bonds and groups do not coincide with each other.

Optical Activity

The ability of a chiral compound or drug to rotate the plane of polarized light.

Plane Polarised Light

Light that travels in only one direction; it is essential for the operation of a polarimeter.

Meso Compound

A compound that has an internal mirror plane of symmetry ($\sigma$) such that one half is a reflection of the other; it is optically inactive despite having chiral carbons.

Saw-horse Model

A diagram used to depict a specific conformation of a molecule, such as the staggered conformation of ethane ($C_2H_6$).

Newman Projection

A visualization of the conformation of a chemical bond from front to back, representing the front atom as a dot and the back carbon as a circle.

Proximal Atom

The front carbon atom in a Newman projection representation.

Distal Atom

The back carbon atom in a Newman projection representation.

Eclipsed Conformation

A conformation where groups on the proximal and distal carbons are thrown close together, resulting in a dihedral angle of $0^{\circ}$.

Staggered Conformation

The lowest energy conformation where groups on the front and distal carbons are furthest apart, with a dihedral angle of $180^{\circ}$.

Gauche Conformation

A conformation where the groups on the proximal and distal carbons are at a $60^{\circ}$ angle to each other.

Dihedral Angle

The angle between a sigma bond on the front carbon and a sigma bond on the back carbon in a Newman projection.

Torsional Strain (Eclipsing Strain)

The energy difference caused by increased electrostatic repulsion of eclipsing bonds; in ethane, this is approximately $3\,kcal/mol$ ($12\,kJ/mol$).

R (Rectus)

A configuration designation meaning 'to the right' or clockwise.

S (Sinister)

A configuration designation meaning 'to the left' or anti-clockwise.

Fischer Projection

A formula using vertical and horizontal lines where horizontal bonds are in front of the plane and vertical lines represent bonds behind the plane.

Cahn-Ingold Prelog Convention

A system used to assign (R) or (S) configurations to chiral carbons based on the priority of bonded groups by atomic number.

Sodium D Line

One of the yellow emission lines in the spectrum of sodium used as monochromatic light for polarimetry.

Dextrorotatory ($d$ or $+$)

A drug molecule or compound that rotates the plane of polarized light to the right.

Laevorotatory ($l$ or $-$)

A drug molecule or compound that rotates the plane of polarized light to the left.

Specific Rotation ($[\alpha]$)

The rotation found using a $10\,cm$ ($1\,dm$) sample cell and a concentration of $1\,g/ml$, calculated as $[\alpha] = \frac{\alpha_{(observed)}}{c \times l}$.

Racemic Mixture (Racemate)

A mixture containing equal amounts of dextro ($+$) and laevorotatory ($-$) isomers, making it optically inactive; denoted by $(\pm)$ or $(d,l)$.

Diastereomers

Stereoisomers that are not mirror images of each other.

Optical Purity ($o.p$)

The ratio of the observed rotation of an enantiomeric mixture to the rotation of a pure enantiomer, expressed as a percentage.

Enantiomeric Excess ($e.e$)

A method for expressing the relative amounts of enantiomers in a mixture, calculated as $\frac{d-l}{d+l} \times 100\%$.