OCHEM 1 importants Flashcards
An atom with a _______, _______, _______ charge that is “one away” from a _______ or _______ can be involved in resonance
lone pair, positive, negative
double or triple bond
What is the one exception to the resonance rule?
Lone pair one away form positive charge
The MAJOR resonance contributor is determined by what three rules?
1) Octet satisfied
2) minimized amount of charges
3) negative charge on most EN atom
When resonance is possible, the _______ hybridization option will be the truth
lower
what 3 physical properties are affected by intermolecular forces?
1) boiling point
2) melting point
3) solubility
What are the 3 intermolecular forces from strongest to weakest?
1) hydrogen bonding
2) dipole dipole
3) London dispersion (van der Waals)
Boiling point is affected by dispersion forces through _______
surface area
- larger surface area = higher boiling point
What is the rule for solubility?
like dissolves like
The higher the pKa the _____ the acid
weaker
1) Ka»>1 = _______
2) Ka«<1 = _______
1) strong acid
2) weak acid
When determining the direction of the equilibrium reaction arrow, the ______ reacts first
STRONG REAGENT
- lower pKa (look at acid and conjugate acid)
The stability of the _______ is a good guide to acidity
conjugate base
What are the 4 steps to determining acidity?
1) Atom EN
2) resonance (quality over quantity)
- while looking at CB
3) Inductivity (EDG or EWG)
4) hybridization
explain the inductive effect on acidity
2-10
it decreases the farther the partial positive is from the full negative
How do you differentiate EDGs and EWGs
EDG will have lone pairs and or negatives directly connected to main chain
EWG will have partial positive or positive directly connected to main chain
- Halogens are EWGs
explain the effects of hybridization on acidity
sp3 < sp2 «_space;sp
What is the only time where size determines acidity and how?
hydrogen halides (HF<HCl<HBr<HI)
Oxygen vs sulfur (SH>OH)
nucleophiles are electron _______
donors
electrophiles are electron _______
acceptors
sigma bonds are allowed to rotate leading to conformations of energy differences, what are the newman conformations of a butane?
think mercedes benz
1) totally eclipsed
2) gauche
3) eclipsed
4) anti
What are the two types of strain possible for linear alkanes? Which is preferred?
1) steric
2) torsional
- steric is preferred over torsional
What are the two types of strain that make up ring strain?
1) angle strain
2) torsional strain
What are the 3 types of cyclohexane conformations?
1) chair (lowest E)
2) boat (highest E)
3) twist-boat (mid E)
substituents in cyclohexane chair conformation can be oriented _______ or _______
1) axial
2) equatorial
What are the 3 steps to radical mechansims?
1) initiation
2) propogation 1 and 2
3) termination
Keq > 1 = _______ reaction favored
Keq < 1 = _______ reaction favored
1) forward
2) reverse
K > 1 is associated with _______ ΔG
K < 1 is associated with _______ ΔG
1) Negative
2) Positive
What is the formula for bond disassociation energy?
the sum of BDE broken - the sum of BDE formed
The rate limiting step or RDS is determined by _______
highest Ea
Hammonds postulate: the structure of the transition state resembles the structure of the closest stable structure in _______
energy
Cahn-Ingold-Prelog priority is determined by _______
atomic number
What are two exceptions to chiral compounds without asymmetric atoms?
1) biphenyls (Ph-Ph)
- only if sterically crowded
2) Allenes (C=C=C)
- end carbons must have different groups
What is the formula to find out how many the max amount of possible stereoisomers in a compound?
(2^n) - lines of symmetry
What is the key to drawing Fischer projections?
1) Draw skeletal with stereochemistry
2) newman projections with longest carbon chain at tops (totally eclipsed)
3) fischer projections
Describe geminal and vicinal dihalides
geminal are on the same carbon while vicinal are on neighboring carbons
What is the only situation where alkyl halides are less dense than water?
only alkyl fluorides and chlorides
SN2 reactions are _____-step reaction, while SN1 reactions are _____-step reactions
one (concerted)
multiple (C+ intermediate)
SN2 reactions have ____ molecule(s) in r.d.s
2
What are the 3 characteristics of a good leaving group?
1) electron-withdrawing
2) stable once they have left
3) polarizable to maintain partial bonding in TS
Good leaving groups should be _______ bases; therefor, they are the conjugate bases of _______ acids
weak
strong
What determines the rate of SN2 reactions?
1) steric hindrance (slows)
2) resonance (speeds)
SN1 reactions have ____ molecule(s) in r.d.s
1 (electrophile)
Only _______ reactions have the [Nuc] component in the rate-determining step; therefore nucleophile strength is important for _______ reactions
SN2
nucleophile trends:
1) charged vs neutral
2) from left to right in the periodic table
3) from top to bottom on the periodic table
4) bulky groups vs nonbulky groups
1) charged is stronger
2) Nucs get weaker
3) Nucs get stronger
4) nonbulky is stronger
What are the differences between polar protic solvents and polar aprotic solvents
polar protic solvents have H-bonding, while polar aprotic solvents don’t
What are the 2 rearrangements possible in SN1 reactions?
1) hydride shift
2) methyl shift
_______: both nucleophile and electrophile within the same molecule, results in cyclizations/ring
intramolecular
When is the only time where the E1 product is not ignored?
dehydration of alcohols with no nucleophile available (H2SO4 and heat)
most E2 reactions follow _______: the more highly substituted alkene is the major product. The only 2 exceptions are:
zietsevs rule:
1) hofmanns rule
2) conjugation
E2 reactions take the H that is _______ when in linear or _______ when a cyclohexane
anti-coplanar
trans-diaxial
What is markovnikovs rule?
when adding H-X to C=C the H will add to the C with more H
Explain the order of acidity of alkanes, alkenes, alkynes, alcohols, and amines (deprotonation)
alkane > alkene > amine > alkyne > alcohol
explain why addition of water to alkynes usually involves keto-enol tautomerization
doesnt form enol intermediate (C=C-OH) cuz C=O stronger than C=C. So it forms keto (C-C=O)
What is the formula for degrees of unsaturation?
[(2C + 2) - H - X + N] / 2
