Lecture Quiz 2- Lectures 5-10 Flashcards
Def: Arrhenius Acid
donates H+ in H2O
-sour, turns litmus pink, reacts w/ metals
Def: Arrhenius Base
donates OH- in H2O
-bitter, turns litmus blue, feels soapy
Is CH3OH an Arrhenius Acid or Arrhenius Base? What about CH3COOH?
both are not arrehenius acids or bases. They can’t lose the OH- because they are a covalent bond - equal sharing
Def: BL acid
donates H+
-almost anything with H
BL acid exceptions
sp3 C-H, 6 e- species like CH3+, BH3
Def: BL base
accepts H+
-should have a lone pair or (-) charge
BL base exceptions
strong acids
Def: Lewis Acid
Accepts e- pair into empty orbital
Fe3+. Zn2+, and Cu2+ are:
Lewis Acids – metal ions
Def: Lewis Base
donate e- pair to an empty orbital (H+)
All BL bases are
Lewis bases
Is CH3+ a BL acid?
No
Def: electrophile
e- loving
-E+
-accepts an e- pair
All BL acids are
Lewis Acids
All electrophiles are
BL acids = Lewis Acids
An atom has a (-) dipole. Is it electrophilic or nucleophilic?
Nu-
An atom has a (+) dipole. Is it electrophilic or nucleophilic?
E+
T/F E+ are an expanded def of acids
T
Def: basicity
abt thermodynamics / delta H
Def: nucleophilicity
abt kinetics/rate/Ea
If a halogen is bonded to H, is it a base?
Not a base but can lose H+ as it donates e- and act as a Nu-
If a halogen is bonded to a C, is it a base?
No and they can’t lose C, so they can’t act as a Nu0
The larger the Ka, the (weaker/stronger) the acid, the (greater/smaller) dissociation
The larger the Ka, the stronger the acid, and the greater the dissociation
The larger the pKa, the (weaker/stronger) the acid
weaker
What is the pKa range for acids?
-10 - +50
The stronger the acid, the (weaker/stronger) the conjugate base.
stronger acid = weaker conjugate base
What 5 things make a stronger acid?
Large
Electronegative
Resonance
More S character
Induction
Acids get stronger as you move (up/down) and (left/right) on the periodic table due to size.
down right
Order from weakest to strongest acid
HF, HI, HBr, HCl
HF, HCl, HBr, HI
A larger atom with a H+ will have a strong/poor orbital overlap for bonds
poor orbital overlap
HCl pKa =
-6
HBr pKa =
-8
HI pka =
-10
Order from weakest to strongest acid:
H2O, HF, CH4, NH3
CH4, NH3, H2O, HF
Why does acidity increase as EN increases
The electronegative atom is already try to hold its e-
What has more acidity? A localized or delocalized charge?
delocalized
-OH pKa
15-18
What’s stronger, ethanol or alcohol?
Alcohol
Why does acidity increase with more reasonance?
The conjugate base is stabilized when the acid loses a proton, by delocalizing the negative charge across multiple atoms, making it less likely to regain the proton and thus enhancing the acid’s ability to donate a hydrogen ion (H+) in solution; essentially, a more stable conjugate base leads to a stronger acid.
Acidity increases as more s-orbital character in _____ orbital
hybrid orbital
Why does acidity increase with more s character?
e- can approach the nucleus
-s orbital e-‘s at the nucleus have no node through the nucleus
-p orbital e-‘s can’t be at the nucleus because of it
-More s character = the more (+) and (-) chargers can attract
Order from weakest to strongest acid:
alkyne, alkane, alkene
1st Alkyne - 3 bond – has 50% S
2nd Alkene - 2 bonds – has 33% S
3rd Alkyne - 1 bond – has 25% S
The more (protonated/deprotonated) C is, the stronger the acid
deprotonated
Def Induction:
subtle, more about where in general range of specific groups is rather than a new pKa range
-a long range EN model of effects of neighbors through as pi bonds
What are 3 examples of induction
-A neighbor with a larger EN = larger effect, pulls away from H making it easier to dissociate
-A lot of neighbors having large effect.
-A neighbor that is closer
Carboxylic acid pKa:
3-5
Alkane pKa:
~50
Alkene pKa:
~44
Alkyne pKa:
~25
List the 4 types of hydrocarbons
alkane, alkene, alkyne, and aromatic/arene
What hybridization are all of the C atoms in an Alkane? Alkanes only have what type of bonds?
sp3 – sigma bonds
What hybridization are all of the C atoms in an Alkene
sp2 (double bonds)
What hybridization are all of the C atoms in an Alkyne
sp (triple bond)
What functional group has a circle of pi electrons?
aromatic/arene
Heteroatom functional groups have (sigma/pi/both) bonds and every atom is (sp/sp2/sp3) hybridized.
sigma bonds + sp3
What are the 3 types of alkanes?
linear, branched, and cycloalkanes
Simple def of linear alkane
Ex of linear alkanes
2 ends
methane, ethane, propane, butane, pentane
Simple def of branched alkanes
3+ ends
Def: cycloalkane
0 ends
ring
A ring has 8 C’s. What is it called?
cyclooctane
Alkane properties
non-polar
not soluble
-relatively low bp
Boiling point is a measure of
total intermolecular forces
As IMF increases, BP (decreases/increases)
IMC inc, BP inc
What type of forces do alkanes have?
Only dispersion forces - temporary dipoles due to random e- movement
BP increases with
-size
-more atoms
-more dipole
-more surface area
-more dispersion
-more IMF
C10 has (less/more) IMF than C2.
more
Def: staggered
front and back atoms are 60 degrees apart
Def: eclipsed
Front and back atoms are 0 degrees apart
Def: anti
Central atoms are across each other (180 degrees)
Def: gauche
Central atoms are 60 degrees apart, bumping into each other
Def: big groups passing
Used to describe eclipsed conformation where the central atoms are sterically hindering each other
Def: steric hindrance
2 parts of the molecule are bumping / bulkiness bumps into each other
Def: torsional strain
electrons in sp3 of adjacent central atoms line up and repel
Def: torsional angle
60 degrees
Order from lowest E to highest E
Staggered gauche
Eclipsed big groups passing
Stagged anti
Eclipsed
Staggered anti < staggered gauche < eclipsed < eclipsed big groups
T/F We must go through eclipsed conformation to get to staggered conformation
T
Why are all staggered conformations lower in E compared in eclipsed conformations?
Eclipsed conformations have a torsional/eclipsing strain that is higher in E
Why are anti conformations lower in E than gauche conformations?
steric hindrance - prefer structures with fewer gauche groups
Why are large groups passing H lower in energy than large groups passing each other?
due to steric hindrance
Order from least hindrance to most:
1* Carbon, 2* Carbon, and 3* Carbon
1 Carbon, 2 Carbon, and 3 Carbon
3C has the more steric hindrance because it is the bulkiest and takes up the most space
T/F Cyclohexanes are drawn planar but they are actually puckered
T
Each C in a chair has 1/2/3 H atoms
2 H atoms
Each C has one ______ H and one _______ H
1 ax H + 1 eq H
1 up H + 1 down H
T/F axial and eq groups stay the same when rotating bonds in the chair
F
T/F up and down groups switch when rotating bonds in the chair
F
Def: transannular strain
When there is steric hindrance in a chair conformation
What has higher energy? Chair or Boat?
Boat — has a torsional/eclipsing strain
