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Organic Chemistry terms from the ExamKrackers Book


the number of bonds an atom usually forms

formal charge

the number of electrons in the isolated atom, minus the number of electrons assigned to the atom in the lewis structure

index of hydrogen deficiency

the number of pairs of hydrogens a compound requires in order to become a saturated alkane

dipole moment

when the center of positive charge on a molecule or bond does not coincide with the center of negative charge

induced dipole

when the polar molecule/ion creates an electric field, which pushes the electrons and nuclei in opposite directions, which pushes the electrons and nuclei in opposite directions, separating the centers of positive and negative charge

intermolecular attractions

attractions between separate molecules

hydrogen bond

when hydrogen is attached to a highly electronegative atom, a large dipole moment is formed leaving hydrogen with a strong partial positive charge

london dispersion forces

the weakest dipole-dipole force between two instantaneous dipoles

conformational isomers or comformers

different spatial orientations of the same molecule

structural isomer

same molecular formula but different bond to bond connectivity


when a carbon is bonded to four different substituents





observed rotation

the direction and degree to which a compound rotates plane-polarized light

optically inactive

compounds that have no rotation of the plan of the electric field, and have no chiral centers

racemic mixture

chiral compounds that contain equal amounts of both steroisomers

optically active

when plane polarized light is projected through a compound, and the orientation of its electric field is rotated

specific rotation

a standardized form of observed rotation that is arrived at through calculations using observed rotation and experimental parameters


two molecules with the same molecular formula and the same bond-bond connectivity that are not the same compound


same molecular formula, have the same bond-bond connectivity, are mirror images of each other, but are not the same molecule


separation of enantiomers


have the same molecular formula, have the same bond-bond connectivity, not mirror images of each other, not the same compound

meso compound

two chiral centers in a single molecule may offset each other creating an optically inactive molecule


diasteromers that differ at only one chiral carbon


if a ring closure occurs at the epimeric carbon, two possible diasteromers may be formed

anomeric carbon

the chiral carbon of an anomer

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