Mcat Orgo Lecture 1

Front 1

exceptions to octet rule:

Back 1

Boron (B) and Beryllium (Be)

- may contain LESS than an octet

to contain MORE than an octet, the atom must come from the third period (row) or greater

Front 2

Fischer projection:

Back 2

vertical lines ~ orientation INTO the page

horizontal lines ~ orientation OUT of the page

Front 3

Index of Hydrogen deficiency:

Back 3

the number of PAIRS of hydrogen a cmpd requires to be a completely saturated alkane

use the formula 2n +2 - x / 2

where n = # of Carbon's, x = # of H's

- **count halogens as H's, ignore Oxygen, count N as one-half H**

Front 4

alkane prefixes:

Back 4

meth, eth, prop, but, pen, hex, hept, oct, non, dec

Front 5

each additional bond strengthens the *overall* bond and shortens the distance between the atoms

what's harder to break, a single bond or a double bond?

Back 5

- a double bond. It will require more energy to break

(remember, though, that a pi bond is weaker than a sigma bond)

as strength (of the overall bond) increases, length decreases

Front 6

pi bond are more reactive than sigma bonds

Back 6

because they're less stable

only C, N, O, and S commonly form double bonds, and P in ATP

**pi bonds prevent rotation**

Front 7

the closer an electron is to the nucleus, the more stable it is

Back 7

electrons in a pi bond are further from the nucleus;

that's why pi bonds are less stable => more reactive

Front 8

delocalized electrons (b/c of pi bonds) =>

Back 8

resonance structures

**the real mlcl does not shift between these forms**

the real structure is rather a weighted average of all these forms

Front 9

a mlcl with polar bonds may or may not have a dipole moment,

Back 9

b/c dipole moments are vectors and *can cancel out*

Front 10

covalent bonds are the strongest

Back 10

dipole bonds are weaker than covalent

H-bond = strongest dipole-dipole interaction

London dispersion forces = two instantaneous dipoles = weakest type

Front 11

when electrons move toward + charge, energy is lowered

Back 11

you would need to put energy IN to separate them

Front 12

bond energy =

Back 12

average energy required to break a bond

measured as negative; indicates a bond with e's at very low energy => stable bond

**high bond energy = stable bond**

Front 13

isomers =

Back 13

same mlclr formula but different compounds

Front 14

conformers

Back 14

not true isomers

different spatial orientation of the same mlcl

Front 15

structural isomer

Back 15

simplest isomer

same mlclr formula, DIFFERENT connectivity

Front 16

stereoisomers

Back 16

same mlclr formula, same bond-to-bond connectivity

**but NOT the same cmpd**

Front 17

chirality

Back 17

asymmetry such that the structure and its mirror image are not superimposable

so chiral mlcls differ from their reflection, achiral mlcls don't

Front 18

any carbon is chiral if it is bonded to

Back 18

**4 different substituents**

Front 19

the mirror image of a chiral mlcl always has the opposite what?

Back 19

the opposite ABSOLUTE CONFIGURATION

Front 20

relative configuration

Back 20

is not related to absolute configuration

Front 21

observed rotation

Back 21

the direction and degree to which a cmpd rotates ppl

specific rotation is just observed rotation with calculations => more specific

Front 22

optically inactive =

Back 22

does not rotate the E field and thus does not rotate ppl

Front 23

if a cmpd rotates ppl clockwise, it's designated

Back 23

"+" or "d"

left, "-" or "L"

Front 24

stereoisomers

Back 24

same mlclr formula, same bond-to-bond connectivity,

but NOT the same cmpd

two types: enantiomers, diastereomers

Front 25

Enantiomers

Back 25

same mlclr formula, same bond-to-bond connectivity, MIRROR IMAGES OF EACH OTHER,

but not the same cmpd

only difference between them = **opposite absolute configurations at each chiral carbon**

Front 26

enantiomers rotate ppl in opposite directions,

Back 26

to an equal degree

so R-enantiomer rotates +13 degrees, S-enantiomer rotates -13

Front 27

racemic mixture =

Back 27

same amount of left-handed enantiomers as right-handed ones

**racemic mixtures do not rotate ppl**

Front 28

unequal numbers of enantiomers in a mixture =>

Back 28

rotation of ppl to a fraction of the degree that a pure sample would rotate it, the fraction being proportional to the excess

Front 29

resolution =

Back 29

separation of enantiomers

Front 30

**enantiomers have the same chemical and physical characteristics except for these two cases:**

Back 30

1. rxns with other chiral cmpds

2. rxns with polarized light

in these cases, their properties differ from each other

Front 31

diastereomers

Back 31

same mlclr formula, same bond-to-bond

but NOT mirror images of each other

and of course,not the same mlcl

Front 32

cis isomers, when compared to trans, have

Back 32

higher BP, and lower MP

Front 33

steric hindrance =

Back 33

when substituents in the cis position crowd each other

=> higher energy levels => higher heats of combustion

Front 34

are the physical and chemical properties of diastereomers different or the same with respect to each other?

Back 34

different - two diastereomers have different properties

Front 35

meso cmpds

Back 35

when **two chiral centers in a single mlcl offset each other by creating an optically inactive mlcl**

meso cmpds have a plane of symmetry through their centers, which divides them into mirror images
=> achiral => optically inactive

Front 36

epimers =

Back 36

*diastereomers that differ at only one chiral center*

think glucose - when the ring closes on the epimeric carbon, one of two possible anomers is formed: alpha or Beta

the carbon connected to both O's is now called the anomeric carbon