Chem/Phys II Flashcards
bond angles to know: trigonal planar
120 degrees
bond angles to know: linear
180 degrees
VSEPR theory
Valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible
trigonal planar
has 3 binding regions (no electron pairs)
aluminum
is an exception to the quartet rule, makes 3 bonds
bond length is determined by
the sizes (radii) of the two bonding atoms and how many electron pairs they share
SN1 stereochemistry
In an SN1 reaction, the original stereochemistry of the molecule is lost when the carbocation intermediate (a planar structure) is formed. Thus, the product is present as a racemic mixture. Such a mixture includes each enantiomer in a 1:1 ratio, meaning that it promotes no net rotation of polarized light.
epimer
These molecules differ at a single stereogenic center, classifying them as epimers.
anomeric carbon
anomeric carbon (the carbon atom bound to two separate oxygen groups)
E1 reaction-DONT NEED TO KNOW
E1 reactions are unimolecular eliminations. These reactions are analogous to SN1 mechanisms, as both are first-order and involve the formation of a carbocation. As such, both are heavily favored by tertiary reagents. Additionally, use of a mild or weak base tends to push a reaction toward E1, as E2 reactions (which are bimolecular) require moderately strong basic species. Finally, like SN1 processes, E1 reactions prefer protic solvents for carbocation stabilization.
UV-visible spectroscopy
-An analytical technique involving measurement of the UV-visible light absorbed by a substance. -mainly used to analyze conjugated systems
What would PCC oxide an alcohol to?
As a weak oxidizing agent, PCC will oxidize a primary alcohol to an aldehyde. According to IUPAC naming convention, this aldehyde group will be given the highest priority, so our numbering should begin at that end of the chain. The parent alkane is five carbons long, and our high-priority aldehyde is given the suffix “-al,” yielding “pentanal.” From there, the methyl substituents are numbered based on the carbons to which they are attached.
What would CrO3 and K2Cr2O7 turn a primary alcohol into?
strong oxidants and will thus oxidize a primary alcohol directly to a carboxylic acid
addition of pyridine (ring with an N in it)
(a weak base) will decrease the chance of this protonation, inhibiting carbocation formation
which is a better acid ethanol, or ethanthiol
Since sulfur is much larger than oxygen, the conjugate base of ethanethiol is better able to delocalize negative charge, increasing its stability. Remember, the more stable the conjugate base, the stronger the acid.
SN2
These processes, formally known as bimolecular nucleophilic substitution reactions, happen in one step and involve a “backside attack” by a strong nucleophile. Since the attacking atom must bind at the same time as the leaving group is removed, these reactions require an unhindered substrate.
good leaving groups are
weak bases
Can acetals form under basic conditions?
No, acetals cannot form under basic conditions. Under basic conditions, only hemiacetals can be formed. Acetals, which result from the reaction of a hemiacetal with an alcohol, require acidic conditions.
Hemiacetals and hemiketals exist in equilibrium with
aldehydes and ketones.
alpha hydrogen
An alpha hydrogen is one that is bound to the carbon immediately adjacent to a carbonyl carbon
chromic acid
Chromic acid (H2CrO4), like many chromium-containing reagents, is a strong oxidizing agent. Reaction of a primary alcohol with such a compound will oxidize it as thoroughly as possible. Since a primary alcohol has only one bond to carbon, it possesses the ability to form three bonds to oxygen, creating a carboxylic acid.
reducing agent NaBH4 turns an aldehyde into?
could turn an aldehyde into an alcohol
kinetic v thermal product
The kinetic product is the one that is less thermodynamically stable, but is easier to synthesize due to a lower activation energy. In general, kinetic enolates are less substituted than their thermodynamic counterparts. Here, the double bond has formed in the position that is less sterically hindered (between carbons 1 and 6).If this were the thermodynamic enolate, it would have the double bond between carbons 1 and 2 (the more substituted position adjacent to what formerly was the carbonyl carbon).
reducing agents
-Chemically, deuterium and hydrogen behave identically. Thus, lithium aluminum deuteride may be considered to be equivalent to lithium aluminum hydride (LAH). LAH is a strong reducing agent and is certainly capable of reducing both carboxylic acids and aldehydes. It would therefore be the most appropriate choice. -Sodium borohydride would be perfectly adequate for selective reduction of the aldehyde, but it lacks the reducing power necessary to reduce the carboxylic acid. -Sodium hydride is a strong base, but is not a hydride source and thus is not a reducing agent. -Potassium cyanide is a nucleophile and a weak base. It is not an appropriate choice for any reduction reactions.
Thionyl chloride (SOCl2) is a
reagent commonly used to convert carboxylic acids into acyl halides
Reaction of a carboxylic acid with an alcohol forms an
ester. Esters are nearly identical to carboxylic acids in terms of reactivity.
halide leaving group stability
iodine serves as the best leaving group. To understand this concept, consider the periodic table. As a member of a much lower period than (for example) fluorine, iodine is a very large atom. As such, it can easily delocalize the negative charge gained when it exits as a leaving group. The better the leaving group, the more reactive the compound, and a more reactive molecule is by definition less stable.
Reactivity of carboxylic acid derivatives
acid anhydride, one of the more reactive of the carboxylic acid derivatives. Esters, in contrast, are moderately unreactive, since their leaving groups are extremely unstable in solution
When cyanide reacts with propanal (an aldehyde), it forms a
cyanohydrin. Interestingly, it is the carbon - not the nitrogen - atom that acts as a nucleophile to attack the carbonyl carbon. The final cyanohydrin product consists of the former carbonyl carbon bound to -OH, -H, the original -R group from the aldehyde, and -C≡N.
Charles’ law states
that the volume of a gas is directly proportional to its temperature
Dalton’s law
Dalton’s law states that the total pressure in a vessel is the sum of the partial pressures of the components. Moreover, the partial pressure of a gas is proportional to its mole fraction in the container.
As increasing amounts of NaCl are added to water
boiling point will increase, melting point will decrease, and vapor pressure will decrease.
metathesis reaction is synonymous with
a double displacement reaction in which two reactants exchange cations (also could think of it as two reactants switching anions)
how to calculate oxidation state
https://www.khanacademy.org/science/chemistry/oxidation-reduction/redox-oxidation-reduction/v/practice-determining-oxidation-states (a hint that oxdation is occurring is if large amounts of oxygen are present)
Avogadro’s number
6.02 x 10^23
What is Keq?
[products]/[reactants] at equilibrium so if greater than 1 favors products
Keq for reverse reaction
1/Keq
Q is the reaction quotient
-it is the same formula as Keq, but the concentrations come from any point in time, not just during equilibrium -so if Q
Le Chatelier’s Principle
States that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress. stress= change in reactant or product concentrations, temperature, pressure, or volume
if change in H is negative
the reaction is exothermic
if a reaction is exothermic, then heat is a ___
product
specific heat capacity
q=mcdeltaT
change in H reaction
ERROR!
Gibbs free energy
ERROR!
exergonic reaction
Reaction that proceeds with a net release of free energy, so gibbs free energy is negative and reaction is spontaneous *to clarify beign spontaneous does not mean anything about the kinetics, or rate of reaction
rate is a kinetic parameter and is largely determined by
activation energy (affected by enzyme catalysists)
delta G of rxn =
-RTlnK R=8 T=kelvin ln(1)=0
thermodynamic product
-is more stable -forms more slowly (favored when temp is high bc has enough energy to overcome the high activation energy barrier)
kinetic product
-forms more quickly -less thermodynamically stable -lower activation energy -favored at low temperatures
heat equation for for temperature change (not phase change)
q=mcdeltaT q=heat m=mass c=specific heat capacity of a substance (varies depending on the phase) delta T= temperature
volume and temperature of a gas are directly proportional under constant pressure
V1/T1=V2/T2
Ideal Gas Law
PV=nRT n=number of mols R=.08206L(atm)/(k)mol
molality
mols of solute/kilograms of solvent
Normality
molarity x # of H’s in the acid
assumptions about ideal gasses:
-average KE is proportional to T -particles have no volume -particles exert no forces on each other
nucleoside
nucleotides that lack attached phosphate groups
substitution solvents
polar-facilitates polysubstitution nonpolar-facilitates monosubstitution
acetal v hemiacetal
Hydrolysis of the acetal will yield a free aldehyde and two alcohols
Tollen’s reagent
-detects presence of reducing sugar (if reducing silver is present then a silver coating forms) -uses Ag(NH3)2+ as oxidizing agent *in a + test, aldehydes reduce Ag+ to metallic silver
cholesterol in physiological conditions
In eukaryotic cells in vivo, the role of cholesterol in the membrane is to provide fluidity within the otherwise rigid phospholipid structure.
UV-Vis
typically used to assess the presence of highly conjugated systems
Mass spectrometry peaks represent
mass-to-charge ratios. More specifically, mass spec involves the fragmentation and ionization of the molecule in question. Typically, this ionization simply entails the removal of one electron, leaving the mass of the fragment virtually unchanged.
During a phase change, the temperature of a substance
stays the same
the rate constant can be affected by:
activation energy and temp
catalysis act by
reducing the activation energy (only affect kinetics not thermodynamics)
Rate laws are determined by
experiment
for a radical to form…
there usually needs to be an odd number of valence electrons in the molecule
heterogenous catalyst
a catalyst whose phase is different from the reactants’, ex. a gas catalyst for a liquid reaction
can reason out rate law constant (k) units, rate itself is M/s (which is on left side of equal sign)
then you just plug in molarity on the right side where there are concentrations
Arrhenius acids
produce H+ ions in water
Arrhenius base
Produces OH- ions when dissolved in water
Bronsted-Lowry acid
proton donor
Bronsted-Lowry base
proton acceptor
Lewis acid
electron pair acceptor (electrophiles - Bf3, BCl3, AlCl3, and AIF3)
Lewis base
electron pair donor
Amphiprotic
A species that can either accept or donate a proton, so can act as either and acid or a base, ex. H2O which can become OH- or H3O+ also amino acids are an example
amphipathic
having both a hydrophilic region (polar) and a hydrophobic region (non polar)
Ka and Kb constants, (dissociation constants of acids and bases)
ratio of concentration of products to reactants, so the higher it is the stronger it is bc it has more dissociation
strong acids
HCl, HBr, HI, HClO3, HClO4, HNO3, H2SO4 (not strong acids: HF, H2CO3, H3PO4)
Strong bases include
LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
pOH
-log[OH-]
pH
-log[H+]
when using pH scale, a shortcut to calculating pH is that if the concentration of [H+] is written in scientific notation, then the pH is the negative of the exponent
1 x 10^-4 pH would be 4
pKa vs Ka
higher ka is a stronger acid but smaller pKa is a stronger acid, same relationship is true for bases, because K always refers to the disassociation (ratio of products to reactant concentration)
(Ka)(KB)=
Kw=10•-14
pKa+pKb=
pKw=14
ICE table
Initial, Change, Equilibrium
ICE tables what to add/subtract
https://www.youtube.com/watch?v=54n1XppP-lA
For elementary reactions (or single-step), stoichiometric coefficients can be used to write the
rate law These coefficients become exponents according to the following theoretical example: for the reaction aA + bB → cC, rate = k[A]a[B]b.
Keq can be found by
placing products over reactants, with each species raised to an exponent corresponding to its coefficient in the chemical reaction. (Note that all concentrations must be at equilibrium.) Solids and pure liquids are not included in this expression.
Ksp
read this: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Solubilty/Solubility_Product_Constant%2C_Ksp
As an equilibrium constant, Ksp only responds to changes in
temperature
The lower the value of the pOH of a solution, the more _____ the solution is.
basic (akaline)
what forms a good buffer?
Equimolar amounts of a weak acid and its conjugate will form an ideal buffer. -not strong acids/bases
relationship between pKa and Ka
pKa = -log(Ka)
pH=
-log[H+]
Henderson-Hasselbalch equation can be written as either
pH = pKa + log([A-]/[HA]) or pOH = pKb + log([HA]/[A-])
less positive oxidation potential= less likely to oxidize
less positive oxidation potential; in other words, it is less likely to oxidize and the oxidation potential and reduction potential are inverses of each other
electrolytic cell has to do with the reduction potential and you need to know wthat reduction occurs at the___
cathode reduction potential higher=more likely to be reduced and thus act as an oxidizer In electrolytic cells, the nonspontaneous redox half-reaction will take place thanks to the external current being applied. Since Al3+ has a more negative reduction potential than Cd2+, it is Al3+ that will reduce and Cd (s) that will oxidize. In contrast, in a galvanic cell, the reverse (spontaneous) redox half-reaction would take place. Oxidation and reduction always occur according to the mnemonic “REDCAT”: reduction happens at the cathode and oxidation takes place at the anode.
IR O-H stretching region
3000 to 3700 cm-1,
IR C-H stretching region
2800 to 3000 cm-1
IR C=O stretching region
1700 to 1800 cm-1
IR C-O stretching region
1200 to 1400 cm-1
LAH (lithium aluminum hydride) is a strong
reducing agent changes things to alcohols
endergonic
ΔG is negative and the reaction is spontaneous
Gibbs free energy
deltaH-T(deltaS)
Henderson-Hasselbalch equation
pH = pKa + log [A-]/[HA]
pI (isoelectric point)
when an amino acid or other compound has no charge, find it by averaging the 2 most similar pKas of the molecule
Lewis acid/base
acid: electron pair acceptor base: electron pair donor
Arrhenius acid/base
Acid: produces H+ Base: produces OH-
Bronsted-Lowry acid/base
Acid: proton donor Base: proton acceptor
naming of acids that do not contain oxygen
use prefix “hydro” and suffix “-ic acid”
for acids with oxygen naming depends on the number of oxygens
H plus an element: per_____ic acid -ate -> _____ic acid -ite -> _____ous acid hypo____ous acid
Kw is temperature-dependent but
[H3O+] = [OH-] in pure water