Mcat Ochem

Front 1

Lewis Dot Structure

Back 1

1. find total number of valence electrons for all atoms in molecule
2. use one pair of electrons to for on bond between each atom
3. arrange remaining electrons around the atoms to satisfy the duet rule for hydrogen and the octet rule for other atoms

Front 2

valence

Back 2

number of bonds usually formed

carbon= 4
Nitrogen=3
Hydrogen and halogens= 1

Front 3

formal charge

Back 3

number of electrons in the isolated atom- the number of electrons assigned to the atom in lewis structure

Front 4

index of hydrogen deficiency

Back 4

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

((2n +2) -x)/ 2 n=number of carbons
x= number of hydrogens

Front 5

rules for nomenclature

Back 5

1. longest carbon chain with the most substituents determines name
2. end carbon closest to a carbon with a substituent is always the first, if tie, look to next substituent
3.any substituent is given the same number as its carbon
4. if the substituent is used more than once, use the prefix di-, tri-, tertra-, etc
5. order substituents alphabetically

Front 6

electrostatic forces

Back 6

forces between the electrons and nuclei that creates all molecular bonds

Front 7

sigma bond

Back 7

forms when the bonding pair of electrons are localized between two bonding atoms. Has the lowest energy and is most stable. (single bond= sigma bond and double and triple bonds contain one sigma bond)

Front 8

pi-bond

Back 8

additional bond between two sigma bonded atoms. the orbital of the first pi bond forms below the sigma bond, if another pi bond is formed, it is on either side of the sigma bond. each additional bond shortens the distance between atoms

-pi bonds are weaker than sigma bonds, but when added to sigma bonds, it strengthens the overall bond
-pi bonds prevent rotation

Front 9

Rules for writing resonance structures

Back 9

1. pi bond cannot be moved
2. number of unpaired electrons must remain constant
3. resonance must lie in the same plane
4. only proper resonance structures are allowed

most stable structure most likely to occur

Front 10

conditions for resonance

Back 10

1. a species must contain an atom either with a p-orbital or an unshared pair of electrons
2. that atom must be single bonded to an atom that possesses a double or triple bond

Front 11

dipole moment

Back 11

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

-molecule/ bond with dipole moment= polar
-instantaneous dipole moment possible in nonpolar molecules because electron move about their orbitals and at any given moment might not be evenly distributed

Front 12

London dispersion forces

Back 12

result from instantaneous dipole moments in nonpolar molecules; responsible for phase change in nonpolar atoms (weakest force)

Front 13

conformational isomers (conformers)

Back 13

different spatial orientations of the same molecule

Front 14

structural isomers

Back 14

have same molecular formula, but different bond to bond connectivity

Front 15

chirality

Back 15

differ from their reflections, are mirror images

occur at carbon that has 4 different substituents

Front 16

absolute configuration

Back 16

R= right, S= left

atoms attached to a chiral center are numbered from highest to lowest priority, based on atomic weight (largest=highest)

Front 17

relative configuration

Back 17

differ only by one substituent and are oriented identically about the chiral carbon

Front 18

observed rotation

Back 18

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

Front 19

enantiomers

Back 19

have same molecular formula, have same bond to bond connectivity, are mirror images of each other, but are not the same. have opposite absolute configurations at chiral carbon, and opposite reactions to plane-polarized light

Front 20

optically inactive

Back 20

no molecular orientation is favored so no rotation. caused by compound with no chirality or with an each mixture of both chiral compounds (racemic)

Front 21

diastereomers

Back 21

same molecular formula, same bond to bond connectivity, but are not mirror images and are not the same compound