Chem/Ochem Review Flashcards
(246 cards)
1
Q
NADH/NADPH are what type of agents
A
Reducing
2
Q
What does a hydrolase do?
A
Cuts with water
3
Q
A dehydrogenase…
A
dehydrates-takes away a hydrogen
4
Q
What type of bonding occurs between DNA base pairs?
A
Hydrogen and Van Der Waals
5
Q
Kinetically favorable
A
low activation energy
6
Q
Thermodynamically favorable
A
products have lower energy than reactants
7
Q
G and C pair between ____ Hydrogen bonds, and A and T pair between ____ Hydrogen bonds.
A
3, 2
8
Q
Hydride
A
Anion of Hydrogen: H-
9
Q
Gibbs free energy equation
A
^G=^H-T^S
^H=enthalpy change
^S=entropy change
10
Q
Blood flow equation
A
Q=AV Q=flow rate, A=cross sectional area, V=velocity of fluid
11
Q
Velocity changes ____ m/s while airborn
A
10m/s
12
Q
Average velocity is equal to
A
Vf+Vi/2
13
Q
Deuterium
A
Deuterium is one of two stable isotopes of hydrogen. The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutron in the nucleus. (is uncharged).
14
Q
Photon
A
When emitted, energy is released.
15
Q
Henderson-Hasselbalch eq
A
pH = pKa - log([HA]/[A-])
for every 1.0 unit difference between the pKa and the pH, the ratio of acid to base (or base to acid) will change by a factor of 10 (and following that trend, for every 2 units it would differ by a factor of 100, for every 3 units by a factor of 1,000 and so on).
16
Q
Pka to PH
A
If PKa -> PH, equation shifts to right, acids.
If Pka Acids
17
Q
Le Chatelier’s Principle
A
The attempt for an equation to restore equilibrium.
in CO2 + H2O ↔ HCO3- + H+, if the [H+] increased, the equation would shift left to balance and more CO2 would result.
** Equilibrium expressions are written as products over reactants.
18
Q
Color spectrum
A
390nm————————–700nm
violet, greens, blues, etc, red
19
Q
induced-fit mechanism
A
proposes that the enzyme stabilizes the transition state of the substrate, causing a reduction in the activation energy of the transition state.
20
Q
lock and key mechanism
A
In this analogy, the lock is the enzyme and the key is the substrate. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).
21
Q
Michaelis-Menten kinetics equation:
A
V0 = Vmax[S]/(KM + [S])
22
Q
Sucrose:
A
Formed by 1 glucose and 1 fructose. Glucose forms a 6 membered ring while fructose forms a 5 membered ring
23
Q
Oligomer:
A
A few monomer units combined, but not unlimited like a “polymer”
24
Q
Oxidation/Reduction:
A
If something is oxidized (loss of electrons) then it is a reducing agent. Vice versa
25
D (dextrorotary):
| L
D: Rotates light clockwise.
L: Rotates light counterclockwise
26
Metals:
THINK OF METALS AS: larger atoms with loosely held electrons. Metals “like” to lose
electrons and form positive ions. They are lustrous, ductile, malleable and excellent conductors of both
heat and electricity. They are involved in ionic bonds with nonmetals. Are good reducing agents.
Have lower electronegativities.
27
Non Metals:
THINK OF NON-METALS AS: smaller atoms with tightly held electrons. Non-metals
“like” to gain electrons and form negative ions. They have lower melting points than metals, and form
covalent bonds with non-metals. Most of the O-Chem stuff involves non-metals. Form oxides that are acidic.
Are good oxidizing agents.
28
The smaller the atom, the ___:
more electronegative, have a higher ionization energy, greater electron affinity and less metallic character than a larger atom.
29
Electron affinity:
the amount of energy released or spent when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion.
30
Electronegativity:
a measure of the tendency of an atom to attract a bonding pair of electrons.
31
Ionization energy:
the amount of energy required to remove the most loosely bound electron, the valence electron, of an isolated gaseous atom to form a cation. (+)
32
Work Function:
Bombarding certain metals with energy can cause the ejection of an electron from their outermost shell (i.e., valence electron). The work function
refers specifically to valence electrons being ejected from the surface of a solid metal. If the energy
added is less than the work function, the electron won’t be ejected. If it is greater than the work function, the excess energy will be transferred into the kinetic energy of the ejected
electron.
KE = E – φ , E = hf
33
Electron Emission:
One of the most important take-home messages is that more INTENSE light [i.e., same wavelength, but more photons striking the metal per second] does NOT increase the KE of ejected photons, but DOES increase the number of photons ejected. Meanwhile, changing to a higher frequency light [i.e., blue light replacing red light] DOES increase the KE of the ejected electrons [as long as the work function has been exceeded].)
34
Half life:
The half-life of a substance (t1/2) is the amount of time required for exactly one-half of the mass of that substance to disappear due to radioactive decay.
35
Alpha decay:
The loss of one He nucleus, which has a mass number of 4 and atomic number of 2.
36
Beta Decay:
A neutron is changed into a proton with the ejection of an electron.
37
Electron capture:
A proton is changed into a neutron via capture of an electron
38
Ionic character:
The amount of ionic bonding going on between two atoms. Max amount would be between Florine and Francium, due to largest difference in electronegativity. C-C has almost none.
39
Condosity:
The “condosity” of a solution is the concentration (molarity) of an NaCl solution that will conduct electricity exactly as well as the solution in question
40
7 strong acids:
HCl, HBr, HI, HNO3, HClO3, HClO4, and H2SO4
41
Bond Strength:
```
Energy is always REQUIRED to break a bond. Energy is
always RELEASED when a bond is formed
Stable compounds (e.g., N2) have HIGH bond energies.
Unstable compounds (e.g., ATP) have LOW bond energies
```
42
Heat of combustion:
the amount of energy released when a molecule is combusted with oxygen. All covalent bonds are broken and reformed in a radical reaction. The higher the energy of the molecule (i.e., less stable) the higher the heat of combustion.
43
Coordinate covalent bond:
A covalent bond in which both electrons shared in the bond are donated by one atom. In most cases, more than one of these “donor” molecules surround and bind a single “recipient” molecule. The donor molecule must have a lone pair and the recipient molecule must have an empty orbital
44
Emperical formula vs molecular formula:
Molecular formulas tell you how many atoms of each element are in a compound, and empirical formulas tell you the simplest or most reduced ratio of elements in a compound. If a compound's molecular formula cannot be reduced any more, then the empirical formula is the same as the molecular formula
45
Percent mass:
(mass of one element/total mass of the compound)(100%)
46
hydroxide, nitrate, nitrite, chlorate,
chlorite, hypochlorite, perchlorate, carbonate, bicarbonate, ammonium, sulfate, phosphate,
manganite, permanganate, and cyanide
```
Hydroxide is OH-
nitrate is NO3-
nitrite is NO2-
chorate is ClO3-
perchlorate is ClO4-
chlorite is ClO2-
hypochlorite is ClO-
carbonate is CO32-
bicarbonate is HCO3-
ammonia is NH3
ammonium is NH4+
sulfate is SO42-
phosphate is PO43-
manganate is MnO42-
permanganate is MnO4-
cyanide is CN-
```
47
Combustion reaction:
Combustion reactions take place when a compound containing carbon and hydrogen reacts with oxygen to make water vapor, carbon dioxide, and heat.
CₘHₙ + O₂ → CO₂ + H₂O
48
Synthesis reaction:
simple compounds are combined to make a more complex one.
| 2 Na + Cl₂ →2 NaCl
49
decomposition reaction
where a molecule breaks apart into simpler ones.
| 2 H₂O₂ → 2 H₂O + O₂
50
Single displacement reaction:
when a pure element switches places with an element in a chemical compound.
A + BC → B + AC
51
Acid-base reaction.
If you combine an acid with a base, you’ll get water and something else.
HA + BOH →BA + H₂O
52
Percentage Yield
Percentage Yield = mass of Actual Yield x 100%
| mass of Theoretical Yield
53
How can you increase yield?
1) Start with more reactants (has to include more of limiting reagent)
2) Shift the equilibrium to the right using one of the actions described by Le Chatelier’s Principle
54
Decrease in Pressure:
Equation will shift from low moles to high moles
55
Kinetics:
Kinetics is the study of reaction rate. In other words, how quickly the reaction proceeds. This is usually measured in terms of how fast the reactants disappear by tracking changes in the concentration of the reactants as a function of time. rate, catalysts, enzymes, energy of activation, reaction order, and transition state.
56
Thermodynamics:
the thermodynamics of a reaction reflect the potential reactivity (for example, given infinite reaction time) and includes all measurements of energy flow and relative stability. Keq, Q, entropy, enthalpy, Gibbs free energy, “favorability,” “spontaneity,” “differences in energy between products vs. reactants,” and yield
57
K
Q>K , then the reaction favors the reactants.
58
K>Q
Then reaction favors products. ->
59
Le Chatelier Increase in pressure:
Increasing the pressure on a gas reaction shifts the position of equilibrium towards the side with fewer molecules.
60
Kinetics:
Kinetics is the study of reaction rate. In other words, how quickly the reaction proceeds. This is usually measured in terms of how fast the reactants disappear by tracking changes in the concentration of the reactants as a function of time
61
Thermodynamics:
the thermodynamics of a reaction reflect the potential reactivity (for example, given infinite reaction time) and includes all measurements of energy flow and relative stability.
62
Rate:
is measured as the change in molarity (M) of the reactants per second (M/s)
63
Rate order graphs:
These graphs will only be linear when the reaction has only a single reactant, OR when it is part of a multiple-reactant reaction where the rate is independent of ALL the other reactants
Zero Order: [A] vs. time is linear
First Order: ln[A] vs. time is linear
Second Order: 1/[A] vs. time is linear
64
Catalysts don't affect:
They do NOT change the equilibrium, Keq, enthalpy change, entropy change, Gibbs free energy, or any other thermodynamic properties.
65
Quantum numbers:
-The azimuthal quantum number describes
the subshell where the electron is located.
-The magnetic quantum number specifies
which of the orbitals holds the electron.
-The electron spin quantum number
differentiates between two electrons in the
same orbital.
66
electron configuration of chlorine in NaCl.
configuration of the chloride ion, which will be the same as the nearest noble gas.
67
Determining combustability:
+1 for each carbon, -.5 for each Oxygen
68
Radiation:
Electromagnetic waves emitted from a hot body into the surrounding environment.
▪ Light colors radiate and absorb less
▪ Dark colors radiate and absorb more
69
Heat capacity:
The amount of energy (Joules or Calories) a SYSTEM must absorb to give a unit change in
temperature (J/K or cal/˚C).
o Formula, where C is the heat capacity, q is heat (or other energy) and T is temperature:
▪ C = q/∆T
70
Specific heat capacity:
describes energy absorption for one
individual substance only and is defined per unit mass.
q = mc∆T
71
Calorimeters:
Device used to calculate enthalpy change (∆H).
Coffee cup: q=mc∆T Provides constant pressure (atmospheric)
Bomb: q = C∆T Provides constant volume
72
PV Work
Work is energy transfer via a force (physics), or via a change in volume at constant pressure
(chemistry). PV Work = P∆V (requires constant pressure, any change in volume tells you there is pv work)
73
The First Law of Thermodynamics:
Energy can neither be created nor destroyed.
Isolated system: heat nor mass can be transferred, any changes are considered part of system
closed system: ∆E = q + w, q=heat change w=work done, not included as part of system
74
The second law of Thermodynamics:
o Heat cannot be changed completely into work in a cyclical process.
o Entropy in an isolated system can never decrease.
75
The Third Law of Thermodynamics:
o Pure crystalline substances at absolute zero have an entropy of zero. (would take infinite number of steps)
76
Temperature:
a measure of the average kinetic energy of the molecules in a substance.
77
Boltzmann's constant:
KE = 3/2kBT
78
Celsius to Kelvin:
C + 273.15
79
Enthalpy
Enthalpy = the energy contained within chemical bonds (Joules) we can calculate ∆H for a reaction (i.e., the change in enthalpy) by finding the difference in total
bond energy between the products and the reactants.
80
entropy:
▪ positive ∆S = increased randomness, and thus more energy available to do work.
▪ negative ∆S = decreased randomness, and thus less energy available to do work.
entropy is represented by the capital letter S, and it is a thermodynamic function that describes the randomness and disorder of molecules based on the number of different arrangements available to them in a given system or reaction.
81
Gibbs free energy:
∆G = ∆H-T∆S
∆G = -RTlnK
∆G = the amount of “free” or “useful” energy
available to do work
▪ negative ∆G = Spontaneous process; free energy available to do work.
▪ positive ∆G = Non-spontaneous process; no free energy available; energy is required.
82
Isobaric
means constant pressure.
83
Isotherm
means no heat exchange (i.e., constant
| temperature).
84
Bronsted-Lowry:
```
Acids donate protons (H+); bases
accept protons (H+).
```
85
Lewis:
Acids accept a pair of electrons; bases donate
| a pair of electrons.
86
Amphoteric
substances can act as either an acid or a base (e.g., H2O).
87
pH formula:
pH = -log[H+] or [OH-]
..A solution with a pH of 2 has [H+] = 10-2
while a solution of pH 4 has [H+] = 10-4
88
Acid Dissociation Equation:
HA + H2O H3O+ + A-
| Ka = [H+][A-]/[HA]
89
Ionization of water:
Addition of acid lowers PH, addition of base highers PH
At 25°C, Kw = Ka*Kb
H2O + H2O H3O+ + OH
| the addition of either an acid or a base shifts the equilibrium for the ionization of water to the left
90
Strong Acids:
HI, HBr, HCl, HNO3, HClO4, HClO3, H2SO4, H3O+
NOT HF
91
Strong Bases:
Group 1A hyrdroxides ( NaOH, KOH, etc.), NH2-, H-,
| Ca(OH)2, Sr(OH)2, Ba(OH)2, Na2O, CaO.
92
Titration:
“A strong base is titrated with a strong acid"
| Base is in beaker, Analyte Acid is being added, titrant
93
What is a buffer made up of?
A buffer solution contains a weak acid and weak base, often the conjugates of each other. In a buffer
there is an equilibrium between a weak acid and its conjugate base, or between a weak base and its
conjugate acid.
94
Henderson-Hasselbalch equation
pH = pKa + log[A-]/[HA]
95
Resonance affect on acidity:
More resonance = greater acidity
96
When ranking acidity:
Look at stability of conjugate base
97
Why do less stable molecules release more energy in a combustion reaction?
the energy of the products is always going to be the same (i.e., the energy of CO2 + H2O). Therefore, the higher the energy of the reactant the greater will be
the difference in energy between the reactant and the combustion products.
98
Formula for formal charge:
Formal charge = Valence - assigned (2 for lone pair, 1 for each bond)
99
Huckel's rule of aromaticity:
To be aromatic, a ring must have 4n+2 pi electrons
100
Isomers:
Two molecules are isomers if they have the same molecular formula but are actually different
compounds.
101
Formula to predict number of isomers for a given compound:
2^n n=number of chiral centers
102
Conformational isomers:
These are NOT true isomers! They are the same exact molecule. When a molecule twists or rotates around its bonds these are considered “conformers” NOT isomers.
103
Structural isomers:
Same formula, different bond-to-bond connectivity (For example: 2-methylpentane and 3- methylpentane are both C6H14).
104
Stereoisomers:
Same formula, same bond-to-bond connectivity, but different in the 3-D arrangement of their
substituents. There are two categories of stereoisomers: enantiomers and diastereomers.
105
Enantiomers: Distinguished with R and S
Two molecules with the same molecular formula and the same bond-to-bond connectivity that are non-identical, non-superimposable mirror images. They contain at least one chiral center, so can't have less than 4 groups.
106
Diasteriomers:
Two molecules with the same formula and the same bond-to-bond connectivity that are non-identical, but are NOT mirror images. geometric isomers, epimers and anomers.
107
Geometric isomers:
(cis/trans): cis = same side; trans = opposite sides.
| Z E
108
Stability of carbocations:
3 > 2 > 1
| Rate of reaction: Fastest ---> Slowest
109
Protic solvent:
Has hydrogens bonded to an electronegative atom
110
Strong nucleophile:
Favors Sn2
111
Strong base:
Favors E2
112
E1:
Favors weak bases; 3° carbons only; polar protic solvents
113
Sn1:
Favors poor nucleophiles, 3° carbons only; polar protic solvents
114
E2:
Favors strong, bulky bases
115
Sn2:
Favors good nucleophiles; methyl, 1° or 2° carbons
116
Melting point and boiling point trends:
1) Boiling point increases with increasing chain length and/or molecular weight.
2) Boiling point decreases with increased branching.
3) Melting point increases with increasing chain length and/or molecular weight.
4) Straight-chain alkanes have the highest melting points. Among branched alkanes, however, increased branching increases melting point.
117
Ring strain:
Increases as ring goes above or below 6 carbons. re stabilizes at 10.
118
Formation of an Alkyl Halide from an Alcohol
Via SN2: CH3OH + HCl -> CH3OH2+ + Cl- -> CH3Cl + H2O
| Via SN1: R3COH + HCl -> R3COH2+ + Cl- -> R3C+ + H2O -> R3CCl
119
Oxidation of an alcohol:
▪ 1 ̊ Alcohols -> Aldehydes -> Carboxylic Acids
▪ 2 ̊Alcohols -> Ketones
▪ 3 ̊ Alcohols -> cannot be oxidized further
120
Common oxidizing agents:
O3, Cr2O7, CrO4, KMnO4, Jones, Collins, PCC, PDC, etc.
121
Reduction synthesis of an alcohol:
Reducing agents such as NaBH4, LiAlH4 and H2/pressure reduce a carbonyl to an alcohol. NaBH4 can only reduce aldehydes and ketones; LiAlH4 and H2/pressure can reduce aldehydes, ketones, carboxylic acids and esters.
122
The Pinacol Rearrangement (Polyhydroxyl Alcohols)
vic-diol + hot acid ketone or aldehyde
123
Protection of alcohols:
| so others can react while these are protected
• Protection with TMS: ROH + TMS -> RO-Si(CH3)3
• Protection by MOM (Mothers are very protective! MOM stands for methoxymethyl ether):
ROH + Base -> RO- + CH3OCH2Cl (MOMCl) -> ROCH2OCH3 (RO-MOM)
124
Reaction with SOCl2 and PBr3:
o ROH + SOCl2 -> RCl
| o ROH + PBr3 -> RBr
125
Formation of Tosylates/Mesylates:
Tosyl-Cl + ROH Tosyl-OR + HCl
126
Dehydration of an Alcohol: Synthesis of an Alkene
o CH3CH2OH + H2O CH3CH2OH2
| + CH2=CH2
127
Grignard Synthesis:
Production of an alcohol with extension of the carbon chain
o CH3COCH3 + CH3MgBr CH3COH(CH3)2
Results in an increase in the number of carbons.
128
Ethers:
Very Non reactive, very unlikely to participate in a reaction when acting as a solvent.
129
Epoxides:
Highly reactive due to ring strain, acid catalyzes the reaction by protonating the oxygen making it a better leaving group
130
Are alkenes electron withdrawing or donating?
weak withdrawing
131
Activating and withdrawing groups:
Anything attached directly to a carbon is going to deactivate, anything attached directly to any electronegative atom will activate, unless it has a positive charge.
132
Acidity:
Always look at the stability of the conjugate base. More stable through withdrawing groups = more acidic.
Resonanse stabilizes, increasing acidity
133
Bacisity:
Donating groups increase basicity.
134
Basicity vs nucleophilicity:
Steric hindrance favors basicity over nucleophilicity; nucleophiles must have very little hindrance. Primary nucleophiles are most common. Secondary atoms can often act as bases or nucleophiles, depending on conditions. However, tertiary atoms will only act as bases.
135
Epimers:
pairs of molecules with one or more chiral
| center that differ ONLY by their R/S configuration at ONE of those chiral centers.
136
How does a net dipole affect boiling point?
A dipole creates greater intermolecular forces and increases boiling point.
137
Wavelength of infrared?
around or more than 700nm
138
Wavelength of UV light?
10-400nm
139
Formula to calculate energy of a photon?
E=hc/lamda h=plancks constant c=speed of light (3e8) lamda=wavelength in nm
140
Reducing agent:
an atom or molecule that donates electrons to another atom ormolecule and is itself oxidized in the process
141
Oxidizing agent:
an atom or molecule that accepts electrons and is itself reduced in the process.
142
Oxidation numbers;
```
Oxygen: -2 or (-1 in peroxides)
Flourine: -1
Hydrogen: +1
Alkali metals: +1 (group 1)
Alkaline earth metals: +2 (group 2)
Group 5: -3
Group 6: -2
Group 7: -1
```
143
Electrical potentials:
Electrical potentials tell us the degree to which a species “wants electrons,” or “wants to be reduced.”
o Ag2+(aq) + 2e- Ag(s) E° = 0.80 V
o Cu+(aq) + 1e- Cu(s) E° = 0.52 V
o Ni2+(aq) + 2e- Ni(s) E° = -0.23 V
o Zn2+(aq) + 2e- Zn(s) E° = -0.76 V
''''Positive E = more likely to gain electrons, negative E = less likely to gain electrons
144
Hydrogen half cell:
It is the standard against which all other half reactions
| are compared. 2H+ + 2e- H2 E˚ = 0.00 V
145
Cell potential:
The cell potential, E° cell is the sum of the electrical potentials for the two half-reactions that make up
an electrochemical cell. Remember the following:
▪ Half-reactions always come in pairs—one reduction half-reaction plus one oxidation half-reaction
▪ E° for any oxidation half-reaction is simply the
negative of E° for the associated reduction half-reaction.
DONT FORGET TO CHANGE SIGN WHEN PULLING OFF TABLE!
146
The Galvanic cell: (spontaneous)
o Galvanic cells convert chemical energy into electrical energy. By taking advantage of the difference in reduction potentials between two metals, a current can be spontaneously generated along a wire that connects two metal electrodes submerged in solutions that contain metal ions.
147
Ox redox in an electrochemical cell: (for galvanic and electrolytic) AN OX RED CAT
Reduction always happens at the cathode and oxidation always happens at the anode.
Cathode = (+) ; Anode = (-) True of galvanic cells only,
Cathode = (-) ; Anode = (+) True of electrolytic cells
148
Electrolytic cell: (in electrolytic cell you can look at battery charges to see which side has which charge in system) (NOT SPONTANEOUS)
Essentially, a galvanic cell to which an external voltage is applied, forcing the electrons to flow in the opposite direction.
o Oxidation still occurs at the anode and reduction at the cathode.
o The species with the lower reduction potential will be reduced.
o The cell potential will always be negative.
o The sum of the externally applied voltage (Vbattery) and the negative cell potential (-E° cell), in volts, must be positive.
o Cathode = (-) ; Anode = (+) Note the difference compared to galvanic cells.
149
Concentration cell:
A special type of galvanic cell; The same electrodes and solution are used in both beakers. for a concentration cell, E°cell = 0.00 V
150
The Relationship between Free Energy and Chemical Energy
∆G° = -nFE° we learn: positive E˚ = negative ∆G = spontaneous reaction
Faraday’s Constant = the charge on one mole of electrons
151
The ideal gas law:
PV = nRT
| ▪ R = 0.0821 L*atm/mol*K or 8.314 J/mol*K
152
For gasses at STP, what volume does one mol of gas occupy>
22.4L
153
Variables of an ideal gas at STP: (Standard Temperature and Pressure)
* P = 1 atm
* V = 22.4 L
* n = 1 mole
* R = 0.0821 L*atm/mol*K or 8.31 J/mol*K
* T = 273 K (0°C)
154
The combined gas law?:
P1V1/T1 = P2V2/T2
155
Dalton's law of partial pressures:
Ptotal = P1 + P2 + P3 . . .
156
Effusion and Diffusion (Graham’s Law):
o Diffusion: The process by which gas molecules spread from areas of high concentration to areas of low concentration due to the random motion imparted to them as a result of their kinetic energy and collisions with other molecules.
o Effusion: The diffusion of gas particles through a pin hole. A pin hole is defined as a hole smaller than the average distance a gas molecule travels between collisions.
157
Solid --> Gas
Sublimation
158
Gas --> Solid
Deposition
159
ΔHfusion represents: For any substance, mp = fp
Melting/ freezing
160
ΔHvaporization represents:
evaporation/condensation
161
The triple point:
is the precise temperature and pressure at which all three phases (i.e., states) exist simultaneously in equilibrium with each other.
162
Critical point:
the precise temperature and pressure above which liquid and gas phases become indistinguishable. At this point liquid and gas phases cease to exist, merging into a single phase called a supercritical fluid
163
The critical temperature and critical pressure:
are simply the temperature and pressure at the critical point.
164
How is temperature affected during a phase change?
Once a phase change starts, all of the energy goes into breaking intermolecular forces and none goes toward an increase in temperature.
165
What are the axis' on a phase diagram? (has all three phases, solid far left, liquid up middle, and gas far right, converge at triple point in a Y)
Y= pressure X= temperature
| (has all three phases, solid far left, liquid up middle, and gas far right, converge at triple point in a Y)
166
What are the axis' on a heating curve? (represents going from solid to liquid to gas)
Y= temperature X = heat added or time
167
Vapor pressure definition:
```
Vapor Pressure (Vp) is the partial pressure of the gaseous form of a liquid that exists over
that liquid when the liquid and gas phases are in equilibrium.
```
168
What two quantities are equal when a liquid boils?
A liquid boils when the vapor pressure of that liquid is equal to atmospheric pressure.
169
Raoult's law:
▪ Vapor Pressure w/ a Non-Volatile Solute = (mole fraction of the pure solvent, X)*(Vp of the pure solvent, Vp°) Vp = XVp°
▪ Total Vapor Pressure w/ a Volatile Solute = (mole fraction of solvent* Vp° of the solvent) + (mole fraction of the solute* Vp° of the solute).
170
Henry's law:
The solubility of a gas in a liquid is directly proportional to the partial pressure of that gas over that liquid.
171
Gas solubility:
For gases dissolved in liquids, increased temperature decreases solubility and decreased temperature increases solubility. (opposite for solids)
172
Boiling point elevation:
| Freezing point depression:
The boiling point of a liquid is elevated when a non-volatile solute is added
The freezing point of a liquid is depressed when a non-volatile solute is added
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Osmotic pressure:
A measure of the tendency of water to move from one solution to another across a semi-permeable membrane. It is the side that will receive the water via osmosis that has the higher osmotic pressure. In other words, more solute means more osmotic pressure
Pi = iMRT ; where i = # of ions formed in solution, M is the solute molarity, R is the gas constant,
and T is the absolute temperature.
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Solution chemistry:
A solution is a homogenous mixture of two or more compounds in the same phase. (We usually think of all solutions as being in the liquid, or “aqueous” phase; however, a homogenous mixture of gases is also called a “solution”.)
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Solvent vs solute:
The solute is the substance dissolved into the solvent. Thus solvent is more abundant than solute.
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Colloids:
Colloids are NOT solutions. Colloids are solvents containing undissolved solute particles that are too small to be separated by filtration, but are much larger than the solute particles in a true solution. Colloids scatter light, while true solutions do not. Examples of colloids include paint (a suspension of solid crystals in a solvent) and dust floating in air.
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Ammonium:
Ammonia:
NH4+
| NH3
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Solvation:
is a general term for the process wherein solvent molecules surround a dissolved ion or other solute particle creating a shell.
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Hydration number:
the number of water molecules an ion can bind via this solvation process, effectively removing them from the solvent and causing them to behave more like an extension of the solute
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Hydrate:
an inorganic compound in which water molecules are permanently bound into the crystalline structure
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Measuring and describing solute conentration:
▪ molarity = moles solute/Liter solution
▪ molality = moles solute/Kg solvent
▪ Molarity (M) changes with temperature, but molality (m) does not.
▪ mole fraction = moles solute/total moles solution (solute + solvent)
▪ mass percent = mass solute/total mass of solution * 100
▪ ppm = mass solute/total mass solution * 106
(for ppb multiply by 109)
▪ normality = # of moles of equivalents/Liter solution.
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Solubility:
is the amount of a solute that will dissolve in a given solvent at a given temperature. Temperature is usually specified because for most solids dissolved in liquids, solubility is directly related to temperature.
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Precipitate:
is a solid formed inside of a solution as the result of a chemical reaction, such as the common ion effect
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Saturated solution:
| Unsaturated solution:
is a solution that contains the maximum amount of dissolved solute it can hold.
is any solution that contains less than its maximum amount of dissolved solute.
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Supersaturation:
solutions usually form only when a solution is held at a higher temperature during dissolution (at which Ksp would be larger) and then slowly cooled to a temperature at which Ksp is smaller.
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Solubility product constant, KSP:
defined as the product of the dissolved ions in a saturated solution (i.e., at equilibrium) raised to their
coefficients in the balanced equation.
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Common ion effect:
Addition of a common ion will cause precipitation. If a spectator ion is added no precipitation
will result.
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Soluble compound ions:
nitrate, ammonium, and all alkali metals (Group IA).
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Insoluble compound ions:
unless paired with something from the “always soluble” list above) carbonate, phosphate, silver (Ag), mercury (Hg), and lead (Pb).
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What is a salt?
A conjugate acid or base bonded to an ion of opposite charge that never participates in the reaction.
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Are ethers reactive?
No , they make great solvents because of this fact
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Do electrons release light when thet move up or down an energy level?
DOWN
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IR absorbances:
▪ Carbonyl, C=O 1700 cm-1 sharp, deep
▪ Alcohol, OH 3300 cm-1 broad, separate from CH
▪ Saturated Alkane, CH 2800 cm-1 sharp, deep
▪ Carboxylic Acid, OH 3000 cm-1 broad, overlaps CH
▪ Amine, NH 3300 cm-1 broad, shallow
▪ Amide, NH 3300 cm-1 broad, deep
▪ Nitriles, CN 2250 cm-1 sharp, deep
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What is infrared spec measuring?
Bond vibrations
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What is UV spectroscopy measuring?
When electrons absorb energy and get excited to the next energy level.
-Double and triple bonds absorb UV better, single dont show up
-conjugated systems absorb the most
-
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Mass Spectromotry:
The molecules of the sample are bombarded with electrons causing them to both break apart into smaller pieces and ionize. This will happen in a random way, producing fragments with different masses and charges. These fragments are accelerated through a narrow curved magnet called a “flight tube”
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NMR (Nuclear Magnetic Resonance) Spectroscopy:
This technique is used to differentiate molecules based on the differing chemical environments of their hydrogen nuclei (H-NMR), or the differing environments of their carbon nuclei (C 13-NMR) ATOM MUST HAVE ODD ATOMIC NUMBER OF ODD MASS NUMBER TO REGISTER WITH NMR, GIVING THEM "NUCLEAR SPIN"
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How to read an H NMR:
Area under curve: Indication of how many H atoms there are
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Differences between H NMR and C NMR:
H NMR are lower ppm, closer to 12
| C NMR are higher ppm, 0-220
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C13 absorbances we need to know:
* C – C 0-50
* C – O 50-100
* C = C 100-150
* C = O 150-200
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What layer ends up where in an extraction?
Non polar layer will be less dense and on top of water, polar layer will be more or as dense and below or in the water.
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Distillation Separation:
at least 25˚C apart. 1) Simple Distillation: Heat the mixture in a flask; the liquid with the lower boiling point evaporates first, enters a collecting arm, cools, and drops into a collecting flask.
2. ) Fractional distillation
3. ) Vacuum distillation
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Fractional Distillation:
A fractionating column is placed between the heating flask and the condensing arm. The mixture is heated to slightly above the boiling point of the more volatile liquid. The gas
rises through a column of glass beads or metal shards. This causes any impurities in the vapor (i.e., molecules from the liquid with the higher boiling point) to condense and fall back into the flask, resulting in a better separation. The more volatile component will be above its boiling point and therefore will not condense. This approach allows separation of compounds with boiling points less
than 25˚C apart.
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Vacuum Distillation:
The air inside the apparatus is evacuated to create a vacuum. Vacuum distillation is used because it dramatically lowers the boiling point, allowing you to work
at more manageable temperatures with substances that have much higher boiling points at atmospheric pressure.
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Chromatography:
Separation of one or more compounds by dissolving them in a “mobile phase” and then passing that phase through or across a “stationary phase.” The substances in the mobile phase interact to varying degrees with the stationary phase based on their polarity. The more interaction that occurs between the two phases the slower the substance will move.
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Paper or thin layer chromatography:
Paper chromatography uses paper as the stationary phase. Thin-layer chromatography (TLC) is nearly identical, but uses manufactured glass or plastic sheets coated with silica, alumina, etc.
• Rf = ratio of distance traveled by component /distance traveled by solvent
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Column chromatography:
The mixture to be separated is passed through a column packed with charged glass beads, or some other polar matrix. The solution is collected in fractions at the bottom of the column (i.e., the collecting tubes are changed at regular intervals).
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Ion exchange chromatography:
The column or stationary phase is coated with cations or anions. The mixture is passed through and oppositely-charged ions adhere to the column. The target molecules can then be eluted by washing with a salt solution.
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Affinity chromatography:
Used to isolate a specific molecule or product based on a very specific affinity or binding interaction. For example, it may be that molecules in the mixture react via acid-base
neutralization with molecules on the column. To elute the bound target molecules one must disrupt the binding interaction.
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Gas chromatography:
• A liquid is used as the stationary phase. The mixture is dissolved into a heated gas and then passed through the liquid. Various components reach the exit port at different rates based on 1) boiling point and 2) polarity. Only consider polarity if the two substances have almost
identical boiling points.
• On a gas chromatograph there will be one peak for each unique compound in the mixture.
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Recrystallization:
The desired product (which still contains impurities) is dissolved in the minimum amount of hot solvent necessary to create a saturated solution. The solution is then cooled as slowly as possible. Because pure substances usually crystallize at a higher temperature than impure substances, if the temperature is dropped just below the melting point of the product the crystals
that form will be product and the impurities will remain in solution.
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Carbonyl properties:
Analogue to S=O or N=O, is shorter and stronger than a normal alkene.
1) Partial positive charge on the carbonyl carbon:
2) Alpha hydrogens: (very acidic)
3) Electron donating/withdrawing groups: (donating deactivates, withdrawing makes it more reactive)
4) Steric hindrance: (bulky add ons decrease reactivity)
5) Planar stereochemistry: (if two substituents are different, product will be racemic mixture of R and S)
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Why are alpha hydrogens in carbonyls so acidic?
Because of the resonance structure formed with the conjugate base. Helps them to leave readily.
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What is the name for a ketone substituent in a molecule?
An oxo group
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Formula for formaldehyde, acetaldehyde, benzaldehyde, and acetone
formaldehyde (HCHO), acetaldehyde (CH3CHO), benzaldehyde (C6H5CHO), and acetone (CH3COCH3).
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Which functional group's carbonyl carbon undergo nucleophilic addition? Substitution?
Addition: aldehydes and ketones
Substitution:
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Acetals/Ketals vs Hemiacetals/Hemiketals:
| ONLY REACTIVE IN ACIDIC CONDITIONS
Acetals/ketals have two –OR substituents and hemiacetals/hemiketals have one –OR substituent plus one alcohol substituent (-OH group)
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What is the Rf value of TLC?
Rf value is equal to the distance traveled by the solute/distance traveled by the nonpolar solvent.
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What is an oxoreductase?
They catalyze oxidation reduction reactions
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WHat is a transferase?
They catalyze the transfer of a functional group from one molecule to another
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What is a hydrolase?
THey catalyze the breaking of a bond using water.
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What is an isomerase?
They catalyze atomic rearangements.
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What is the formula for the work energy theorem?
KEinitial + W = KEfinal
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How many protons are translocated in the mitochondrial matrix for each pair of electrons for NADH and FADH2?
NADH: 10
FADH2: 6
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How can we protect ketones and aldehydes from reacting?
React them with a acetal or hemi acetal, or a diol. Once returned to acidic solution they will return to be a ketone or aldehyde.
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What is the aldol condensation reaction?
The condensation of an aldeyde or ketone with another aldehyde or ketone.
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What is the suffix for a carboxylic acid?
| What about if it says ate?
-oic acid
| Ate would be if the proton has been extracted, like going from formic acid to formate.
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Formula for formic acid, acetic acid and benzoic acid?
Formic acid HCOOH
acetic acid (CH3COOH),
and benzoic acid (C6H5COOH).
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Decarboxylation:
The loss of a CO2 molecule from a beta-keto carboxylic acid, leaving behind a resonance-stabilized carbanion
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Esterification:
Reaction of an alcohol with a carboxylic acid to form an ester.
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What three reagents most commonly form acid chlorides when added to a carboxylic acid?
PCl3, PCl5 and SOCl2.
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Are anhydrides electro or nucleophilic?
Very electrophylic on the carbonyl carbons due to resonance stabilization
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Are amides stable or unstable?
The most stable of all carboxylic acid derivatives
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What is the suffix for an ester?
-oate
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Transesterification
Reaction of an existing ester with an alcohol, creating a different ester. Also requires acid catalysis
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Saponification:
Hydrolysis of an ester to yield an alcohol and the salt of a carboxylic acid
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What are the formulas of phosphoric acid, sulfuric acid, and nitric acid?
Phosphoric acid: H3PO4
Sulfuric Acid: H2SO4
Nitric Acid: HNO3
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Ranking of acid derivative leaving groups:
(best to worst): -Cl > -OCOR > -OH > -OR > -NH2
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Properties of an amine:
Amines can act as either bases or nucleophiles. Primary or secondary amines usually act as nucleophiles and tertiary amines always act as bases (because they are too sterically hindered to act as nucleophiles).
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In column chromatography the stationary phase is (polar or non polar) and the mobile phase is (polar or non polar?
Stationary: Polar
Mobile: Non-polar
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Synthesis of Alkyl Amines:
NH3 + CH3Br NH2CH3 + HBr
1) Ammonia acts as a nucleophile, attacking the alkyl halide via SN2 and kicking off the halide ion.
2) The halide ion acts as a base, abstracting a hydrogen to quench the charge on the nitrogen.
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When adding amines to carbonyls:
Prmary amines yield:
Secondary amines yield:
Tertiary amines yield:
Imines
Enamines
DO NOT REACT
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Field lines and currents go from positive and negative:
Just know that
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Units that make up Watt? (W)
Joules/second
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Units that make up Joules? (J)
Newtons x meter
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Units that make up newtons?
m/s^2
