Organic Chemistry Lecture 1: Molecular Structure

Front 1

Formal charge

Back 1

the number of valence electrons on the free (nonbonded) atom minus the number of electrons assigned to that atom in the Lewis structure

Front 2

Index of hydrogen deficiency

Back 2

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

Index of hydrogen deficiency = ((2n+2)-x)/2

n = number of carbons
x = number of hydrogens

**Count halogens as hydrogens, ignore oxygen atoms, and count nitrogen atoms as one half of a hydrogen atom.

Front 3

Electrostatic force

Back 3

Force between the nuclei that create a molecular bond

Front 4

Coordinate covalent

Back 4

One nucleus can donate both electrons

Front 5

σ-bond

Back 5

Forms when the bonding pair of electrons are localized directly between the two bonding atoms; has the lowest energy and is the most stable form of the covalent bond

Front 6

π-bond

Back 6

Additional bonds formed between two σ-bonded atoms; higher energy level, less stable and form a weaker bond; more reactive than a σ-bond

Front 7

Resonance structures

Back 7

A combination of two or more Lewis structures

Front 8

Dipole moment

Back 8

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

Front 9

A molecule or bond which has a dipole moment

Back 9

Polar; results in the difference in electronegativity of its atoms

Front 10

A molecule or bond without a dipole moment

Back 10

Nonpolar

Front 11

Induced dipoles

Back 11

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

Front 12

Instantaneous dipole

Back 12

Electrons in a bond move about the orbital and may not be distributed between the atoms even when the atoms are identical; can exist in a nonpolar molecule

Front 13

Intermolecular attractions

Back 13

Attractions between separate molecules; occur solely due to dipole moments

Front 14

London Dispersion Forces

Back 14

The weakest dipole-dipole force which is between two instantaneous dipoles

Front 15

Hydrogen bond

Back 15

Strongest type of dipole-dipole interaction

Front 16

Isomers

Back 16

Have the same molecular formula but are different compounds

Front 17

Conformational isomers or conformers

Back 17

(Not true isomers) Different spatial orientations of the same molecule

Front 18

Structural isomer

Back 18

Same molecular formula but different bond-to-bond connectivity

Front 19

Stereoisomer

Back 19

Two unique molecules that have the same molecular formula AND the same bond-to-bond connectivity

Front 20

Chiral

Back 20

Impossible to superimpose on its mirror image

Front 21

Absolute configuration

Back 21

Physically describes the orientation of atoms about a chiral center; arranged according to highest priority

R (rectus = right)
S (sinister = left)

Front 22

Relative configuration

Back 22

Differ by only one substituent and the other substituents are oriented identically about the carbon

Front 23

Observed rotation

Back 23

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

Front 24

Polarimeter

Back 24

Screens out photons with all but one orientation of electric field

Front 25

Plane-polarized light

Back 25

Photons with their electric fields oriented in the same direction

Front 26

Specific rotation

Back 26

Take experimental parameters into account

Front 27

Optically inactive

Back 27

Achiral molecules or racemic mixtures are not separated when plane-polarized light projects through the compound and no rotation of the electric field occurs

Front 28

Optically active

Back 28

Chiral molecules are separated when plane-polarized light projects through the compound rotating the electric field

Clockwise = '+' or 'd' for dextrotorary
Counterclockwise = '-' or 'l" for levorotary

Front 29

Observed rotation

Back 29

The direction and number of degrees that the electric field in plane-polarized light rotates when it passes through a compound

Front 30

Stereoisomer

Back 30

Two molecules with the same bond-to-bond connectivity that are not the same compound and have a different spatial arrangement

Front 31

Enantiomers

Back 31

Same bond-to-bond connectivity, same molecular formula, mirror images of each other, but are NOT the same molecule

Front 32

Resolution

Back 32

The separation of enantiomers

Front 33

Diasteromers

Back 33

Have the same molecular formula, same bond-to-bond connectivity, are NOT mirror images of each other and are NOT the same compound

Front 34

Geometric isomer

Back 34

Type of diasteromer that exist due to hindered rotation; have different physical properties

Front 35

Cis-isomer

Back 35

Molecules with substituents on the same side; have a dipole moment

Front 36

Trans-isomers

Back 36

Molecules with substituents on the opposite-side; do not have a dipole moment

Front 37

Steric hindrance

Back 37

Produces higher energy levels resulting in higher heats of combustion

Front 38

Describing geometric isomers

(E? Z?)

Back 38

E = entgegen. Higher priority substituent for each carbon exist on the opposite sides

Z = zusammen. Same side

Front 39

Maximum number of optically active isomers

Back 39

Maximum number of optically active isomers = 2^n

n = number of chiral centers

Front 40

Meso compound

Back 40

Two chiral centers in a molecule that offset each other creating an optically inactive molecule; mirror images through the plane of symmetry; achiral

Front 41

Epimers

Back 41

Diastereomers that differ at only one chiral carbon

Front 42

Anomer

Back 42

A cyclic stereoisomer of a carbohydrate with isomerism involving only the arrangement of atoms or groups at the aldehyde or ketone position

Front 43

Anomeric carbon

Back 43

The chiral carbon of an anomer