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36 Cards in this Set

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exceptions to octet rule:
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
Fischer projection:
vertical lines ~ orientation INTO the page

horizontal lines ~ orientation OUT of the page
Index of Hydrogen deficiency:
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**
alkane prefixes:
meth, eth, prop, but, pen, hex, hept, oct, non, dec
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?
- 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
pi bond are more reactive than sigma bonds
because they're less stable

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

**pi bonds prevent rotation**
the closer an electron is to the nucleus, the more stable it is
electrons in a pi bond are further from the nucleus;

that's why pi bonds are less stable => more reactive
delocalized electrons (b/c of pi bonds) =>
resonance structures

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

the real structure is rather a weighted average of all these forms
a mlcl with polar bonds may or may not have a dipole moment,
b/c dipole moments are vectors and *can cancel out*
covalent bonds are the strongest
dipole bonds are weaker than covalent

H-bond = strongest dipole-dipole interaction

London dispersion forces = two instantaneous dipoles = weakest type
when electrons move toward + charge, energy is lowered
you would need to put energy IN to separate them
bond energy =
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**
isomers =
same mlclr formula but different compounds
conformers
not true isomers

different spatial orientation of the same mlcl
structural isomer
simplest isomer

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

**but NOT the same cmpd**
chirality
asymmetry such that the structure and its mirror image are not superimposable

so chiral mlcls differ from their reflection, achiral mlcls don't
any carbon is chiral if it is bonded to
**4 different substituents**
the mirror image of a chiral mlcl always has the opposite what?
the opposite ABSOLUTE CONFIGURATION
relative configuration
is not related to absolute configuration
observed rotation
the direction and degree to which a cmpd rotates ppl

specific rotation is just observed rotation with calculations => more specific
optically inactive =
does not rotate the E field and thus does not rotate ppl
if a cmpd rotates ppl clockwise, it's designated
"+" or "d"

left, "-" or "L"
stereoisomers
same mlclr formula, same bond-to-bond connectivity,

but NOT the same cmpd

two types: enantiomers, diastereomers
Enantiomers
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**
enantiomers rotate ppl in opposite directions,
to an equal degree

so R-enantiomer rotates +13 degrees, S-enantiomer rotates -13
racemic mixture =
same amount of left-handed enantiomers as right-handed ones

**racemic mixtures do not rotate ppl**
unequal numbers of enantiomers in a mixture =>
rotation of ppl to a fraction of the degree that a pure sample would rotate it, the fraction being proportional to the excess
resolution =
separation of enantiomers
**enantiomers have the same chemical and physical characteristics except for these two cases:**
1. rxns with other chiral cmpds

2. rxns with polarized light

in these cases, their properties differ from each other
diastereomers
same mlclr formula, same bond-to-bond

but NOT mirror images of each other

and of course,not the same mlcl
cis isomers, when compared to trans, have
higher BP, and lower MP
steric hindrance =
when substituents in the cis position crowd each other

=> higher energy levels => higher heats of combustion
are the physical and chemical properties of diastereomers different or the same with respect to each other?
different - two diastereomers have different properties
meso cmpds
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
epimers =
*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