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Organic Chemistry: Stereochemistry and Isomerism

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Terms in this set (24)

  • What is stereochemistry?

    Stereochemistry is the branch of chemistry concerned with the three-dimensional aspects of molecules.

  • Define isomers.

    Isomers are compounds with the same molecular formula but different chemical structures.

  • What are constitutional isomers?

    Isomers with the same molecular formula but different connectivity of atoms.

  • What is chain isomerism?

    Isomers with the same molecular formula but different arrangements of the carbon chain.

  • What is positional isomerism?

    Isomers with the same molecular formula but different positions of substituent groups.

  • What is functional group isomerism?

    Isomers with the same molecular formula but different functional groups due to different atom connectivity.

  • Define stereoisomers.

    Isomers with the same molecular formula and connectivity but different spatial orientation of atoms.

  • What are conformational isomers?

    Stereoisomers interconverted by rotation around a single bond; often called conformers.

  • What are configurational isomers?

    Stereoisomers that differ in spatial arrangement and cannot be interconverted without breaking bonds.

  • What are geometric (cis-trans) isomers?

    Stereoisomers with different relative positions of groups around a rigid structure like a double bond or ring.

  • Describe cis and trans isomers.

    Cis: same groups on the same side; Trans: same groups on opposite sides of a double bond or ring.

  • How do boiling points compare between cis and trans isomers?

    Cis isomers generally have higher boiling points than trans isomers due to polarity.

  • What are enantiomers?

    Stereoisomers that are non-superposable mirror images of each other.

  • Define chirality.

    A molecule is chiral if it is not superposable on its mirror image; it has handedness.

  • What is a chiral center?

    A tetrahedral atom, usually carbon, bonded to four different groups causing chirality.

  • What is a plane of symmetry?

    An imaginary plane dividing a molecule into two mirror-image halves.

  • What is a center of symmetry?

    A point in a molecule where identical components are equidistant on opposite sides along any axis.

  • What are diastereomers?

    Stereoisomers that are not mirror images; can be chiral or achiral and arise from multiple stereocenters.

  • What is the R,S system?

    A method to assign absolute configuration to chiral centers based on priority rules (Cahn-Ingold-Prelog system).

  • How are priorities assigned in the R,S system?

    Atoms bonded to the chiral center are ranked by atomic number; higher atomic number = higher priority.

  • How to assign R or S configuration?

    Number substituents 1-4 by priority, view with lowest priority at back, clockwise = R, counterclockwise = S.

  • What is a meso compound?

    An achiral compound with two or more chiral centers and an internal plane of symmetry, making it optically inactive.

  • How to identify a meso compound?

    Must have multiple stereocenters, an internal plane of symmetry, and stereochemistry that cancels out (R and S centers).

  • What is the maximum number of stereoisomers for a molecule with n chiral centers?

    The maximum number is \(2^n\).