Frequent Mistakes Flashcards
1
Q
What is an acetyl group?
A
CH3-C=O-R
2
Q
What are STP? When are these used?
A
0 T, 1 atm
used for gas law calculations
3
Q
What are standard conditions? When are these used?
A
25 T, 1 atm, 1 m
used in thermochemistry
4
Q
Which have the highest boiling/melting point: saturated or unsaturated fatty acids?
A
Saturated!
5
Q
What is the ONLY reaction element that will be changed by an enzyme?
A
ENZYMES WILL NEVER CHANGE THE POTENTIAL ENERGY, INITIAL STATE, AND FINAL STATE OF A REACTION. THEY WILL ONLY CHANGE THE ACTIVATION ENERGY OF A REACTION (by lowering the energy of the transition state)
6
Q
What happens when you heat an alcohol?
A
Dehydration
7
Q
How does temperature affect KMnO4?
A
hot KMnO4 → VERY strong oxidizing agent → would break double bonds. VS cold KMnO4 → would just add OH groups to the double bond.
8
Q
How do H bonds affect boiling/melting points?
A
H bonding –> stronger intermolecular forces –> stronger surface tension –> higher melting/boiling point
9
Q
What element is lead?
A
Pb
10
Q
What does inert mean?
A
Cannot react with anything!
11
Q
What are the 5 conditions for a compound to be aromatic?
A
- Cyclic
- Planar
- Conjugated
- 4n + 2 pi electrons
- the ring needs at least one unhybridized p-orbital
12
Q
What to do when asked which molecule will have the highest melting point ?
A
Imagine what they would be like at room temperature
13
Q
Which has the highest melting/boiling point: covalent or ionic compounds? Why?
A
Ionic because they have stronger intermolecular interactions
14
Q
What is the exact thermochemistry definition of the boiling point?
A
The temp at which the vapor pressure of the liquid equals the ambient pressure
15
Q
Which compounds have extremely low boiling points?
A
Noble gases
16
Q
Which compounds have very high melting and boiling points?
A
Transition metals
17
Q
What does denaturation mean?
A
Loss of tertiary structure
18
Q
What are the 2 types of denaturation?
A
- Heat
2. Solutes
19
Q
What happens during heat denaturation?
A
The kinetic energy of the protein increases and overcomes the hydrophobic interactions holding the protein together, so it unfolds
20
Q
What happens during solute denaturation?
A
The solute interferes with the forces that hold the protein together directly in the secondary, tertiary, and quaternary structures
21
Q
What is the effect of SDS on a protein?
A
Denaturation by solubilizing proteins
22
Q
What are the 6 factors contributing the a protein’s tertiary structure?
A
- Disulfide links (cysteine)
- Ionic interactions between acidic and basic side chains
- H bonds
- Van der Waals
- Hydrophobic side chains pushed inside
- Proline kinks
23
Q
What bonds does urea break in proteins?
A
H bonds
24
Q
What bonds do salts or pH changes break in proteins?
A
Ionic bonds
25
What bonds does mercaptoethanol break in proteins?
Disulffide links
26
What bonds do organic solvents break in proteins? What are 2 examples?
Hydrophobic forces
| Ethanol and methanol
27
How to determine the limiting reagent?
Need to identify the reactant with the least amount of moles at the beginning of the reaction
28
What is the equil constant for gases equal to?
Kp = (Pc)^c x (Pd)^d / (Pa)^a x (Pb)^b
29
What is the equil constant equal for in terms of rate constants? Where are the rate constants from?
Kc = k1 x k2 x k3 / k-1 x k-1 x k-1
For the rate equations
30
How does a decrease in pressure affect a reaction's equilibrium?
The side with more moles of gas will be favored
31
How does a decrease in volume affect a reaction's equilibrium?
The side with less moles of gas will be favo`red
32
Does an increase in k1 mean an decrease in k-1?
No because a catalyst could increase both reactions
33
How do I know if a compound is an acid or a based based on its Ka?
Ka>10^-7 = acid
34
What is NH3?
A base!
35
What is an imine group?
C=N
36
What does aliphatic mean?
Not aromatic
37
What is tautomerization?
The movement of an alpha H and movement of a double bond
38
What is the purpose of the Benedict's reagent? How does it work? What is its formula?
To detect the presence of a reducing sugar --> red precipitate of Cu2O
Cu(OH)2
39
What is a reducing sugar?
A carbohydrate that is able to be oxidized meaning it contains a hemiketal or hemiacetal
40
What is a lactone? How is it formed? What is lost
A cyclic ester with a carbonyl on the anomeric C
Formed through intermolecular esterification of a molecule with a carboxylic acid and alcohol group
The carboxyl OH is lost, forming H2O
41
What is the purpose of the Tollen's reagent? How does it work? What is its formula?
To detect the presence of a reducing sugar
Precipitate of silver (s)
Ag(NH3)2+
42
What is the purpose of a Grignard reagent? What is the formula? What is a required condition for this to happen?
To add the R group to a molecule: CO2, carbonyl (C=O --> C-OH)
RMgX (halide)
No water, or else the reagent would react with it
43
What is the Henderson-Hasselback equation?
```
pH = pKa + log [base]/[acid]
pOH = pKb + log [HB+]/[B]
```
44
What is a lactam?
A cyclic amide
45
What is a transesterification?
The swapping of the R(-O) group between an alcohol and an ester
46
What is saponification?
The mixing of fatty acids with NaOH or KOH resulting in a salt
47
What is a fatty acid?
Long chain carboxylic acid
48
What kind of compounds can decarboxylate when heated? What is happening here?
Beta keto acids and beta dicarboxylic acids
| One of the carbonyl Os takes the H from the other carboxylic acid
49
How are esters formed?
Nucleophilic acyl substitution with carboxylic acids and alcohols
50
What is a nucleophilic acyl substitution?
Nucleophilic attack at the carbonyl --> opening of the carbonyl --> elimination of the leaving group --> carbonyl reformation
51
What is an esterification reaction?
Condensation reaction between a carboxylic acid and an alcohol
52
What is the formula of an ether?
R-O-R'
53
In what type of solution are nucleophilic acyl substitutions favored?
Basic and acidic solutions
54
What happens when a carboxylic acid reacts with ammonia (NH3)?
Amide formation (condensation)
55
What happens when you heat dicarboxylic acids or 2 carboxylic acids? Explain the mechanism
```
Anhydride formation (condensation)
One OH group attackks the carbonyl of the other
```
56
Should a nucleophile be more or less substituted?
LESS
57
What is LDA?
A strong base
58
What is the least reactive carboxylic acid derivative?
Amides
59
What happens when you mix an amide and water? What if you add a base?
NADA! Not reactive enough. Need for a base or acid --> it will become a carboxylic acid
60
Water + ester = ?
Carboxylic acid
61
What does [something]dimer mean?
Two of the same [something]
62
What is the chemical basis of Markovnikov's rule?
When adding H2O to a double bond: creating the most stable carbocation → addition of the Nu to the most substituted C.
63
How can you test if a molecule is polar?
Try to dissolve it in water
64
What is a benzyl group?
Benzene right with a methyl group
65
What is toluene?
A benzyl = nonpolar solvent
66
What solvent is needed in Grignard reactions? 2 options
THF
67
What is DMF?
Dimethylformamide = polar aprotic solvent
68
Is chloroform a polar or nonpolar solvent?
Nonpolar!
69
Is diethyl ether a polar or nonpolar solvent?
nonpolar
70
How is polarity measured? 2 ways
1. Dielectric constant = permitivity
| 2. Measuring the dipole moment
71
What are polar protic solvents
They contain O-H or N-H bonds
72
How does one form a Grignard reagent?
Alkyl halide + Mg in diethyl ether
73
What is the structure of acetone? Is it a polar or nonpolar solvent?
CH3-C=O-CH3
| Polar
74
What is DMSO?
Dimethylsulfoxide = polar aprotic solvent
75
What is MeCN?
Acetonitrile = polar aprotic solvent
76
What kind of solvent is needed in nucleophile/electrophile reactions?
Polar aprotic solvents
77
What types of solvents are most likely to participate in reactions?
Polar protic solvents
78
What kind of compounds are polar protic solvents? 4 examples
NH3, alchohols, carboxylic acids, and H2O
79
What are the 3 characteristics of an SN1 reaction? What is another name for it?
1. 2 steps (1st one is rate-limiting and the leaving group leaves)
2. Product: racemic mixture
3. More substituted C → the more reactive
Unimolecular
80
What are the 4 characteristics of an SN2 reaction? What is another name for it?
1. 1 step = concerted reaction
2. back-side attack
3. Less substituted C → the more reactive
4. Inversion of relative configuration
Bimolecular
81
How to order from highest to lowest nucleophilicity?
1. Between molecules with the same attacking group: will parallel basicity: the most basic and the most negative will be the better nucleophile
2. Between molecules with different attacking groups: compare the groups by relative electronegativities of the central atom: the less electronegative, the better nucleophile
82
How to order from highest to lowest electrophilicity?
The better electrophile will have a better leaving group:
1. weak bases = conjugate bases of strong acids
2. the more electronegative, the better the leaving group
83
How can one protect aldehydes and ketones from reacting?
By using diols
84
How does replacing an O for an N affect the oxidation state?
Remains the same!
85
How to compare the boiling points of different alcohols?
Longer C chain = more H bonds = more Van der Walls forces = higher boiling point
86
What is the oxidation order of phenols?
hydroquinone (with OH groups)
quinone (with C=O groups)
hydroxyquinone (with both)
87
What is a geminal diol?
two OHs on 1 C!
88
What does imines tautomerize to? Which is the more common tautomer?
Enamines
| Imines
89
What is an enolate?
Carbonyl alkyl is deprotonated (alpha H is removed) and there is a resonance structure with the C=O
90
What is the difference between kinetic and thermodynamic enolates? When is each favored?
Kinetic: happens the fastest (low activation energy→ requires low T)
Thermodynamic: the slowest, the most stable: favored at high temperatures and weaker, smaller bases.
91
What happens during a Michael addition reaction? What does it form?
Base reacts with a molecule with two alpha C=O, the base will deprotonate the C in between the two C=O (usually would not happen to deprotonate off of a C) and then the carbanion will attack an alpha, beta-unsaturated ketone and connects at the beta C
It forms a dicarboxylic acid connected to a ketone
92
How are Ms and Ts used with alcohols? 2 ways`
1. protect them against oxidizing agents
| 2. make them into better leaving groups for nucleophilic attacks
93
Which are more acidic: phenols or alcohols?
Phenols
94
Which are more acidic: alcohols or cyclic alcohols? why?
Alcohols, because the ring is electron donating, making the H less acidic
95
How is an acetal and ketal formed?
Adding alcohols to aldehydes/ketones
96
What happens during an aldol condensation reaction?
Step 1: Adding catalytic base to an aldehyde --> this deprotonates the alpha C, who then attacks the carbonyl to form an aldol
Step 2: dehydration with heat to remove the alcohol group to form a double bond
97
What is an aldol?
A molecule with an aldehyde and an alcohol group
98
What happens during a retro-aldol reaction? What does it require?
1. add OH- and heat to an aldol
| 2. this will break the bond between the alpha and beta carbons of the carbonyl
99
What is a condensation reaction?
2 molecules combine to form a larger molecule and a small molecule is lost
100
Dehydration is a special type of...?
Condensation reaction
101
What is created during the Gabriel synthesis? 2 What is another name for it?
Amino acid synthesis = racemic mixture
| Malonic-ester synthesis
102
What are thee 4 reactants in the Gabriel synthesis? What is the purpose of the last reactant?
1. Potassium phthalimide
2. Diethyl Bromomalonate
3. Alkyl halide
4. Water (to hydrolyze)
103
What is a hydrolysis reaction?
Adding water to a molecule (sometimes causes a split)
104
What are the 3 reaction types in the Gabriel synthesis?
1. SN2
2. Hydrolysis
3. Decarboxylationn
105
What is created during the Strecker synthesis? 2
An amino acid = racemic mixture
106
What are the 4 reactants of the Strecker synthesis? What is the purpose of the 4th reactant?
1. Aldehyde
2. Ammonium chloride (NH4Cl)
3. Potassium cyanide (KCN)
4. Water (to hydrolyze)
107
What are the 3 reaction types in the Gabriel synthesis?
1. Condensation
2. Nucleophilic addition
3. Hydrolysis
108
What happens when you mix an anhydride and ammonia (NH3)?
Cleavage reaction --> amide + carboxylic acid
| Happens with
109
What happens when you add a nucleophile to an anhydride?
CLEAVAGE
110
What happens during a claisen condensation? What does it require?
C-C bond formation between 1 ester and a carbonyl in which the alpha C anion of the carbonyl attacks the carbonyl of the ester
111
Is phosphoric acid a good buffer?
Yes, over a wide range of pH values
112
What molecule is released when the phosphodiesters bonds are formed during DNA synthesis? What happens to it after that?
Pyrophosphate (PPi) = P2O7 4-
| It is then hydrolyzed to form 2 molecules of inorganic phosphate, Pi
113
At physiological pH, which 2 forms of phosphoric acid have the highest concentration?
HPO4 2- and H2PO4 -
114
What is the Arrhenius equation?
k = A. e ^ (-Ea/RT)
115
What is the Farraday constant? What does it represent?
10^5
The amount of charge contained in one mole of electrons
116
What does metal oxidation require?
O2
117
What is 1 Pa equivalent to?
1 N
118
What is 1 N equivalent to?
1 kg . m / s^2
119
Which subshell are electrons removed from when they are removed from an element?
From the subshell with the highest n value
120
What are the 2 exceptions to the electron configuration rules?
Cr and its group and Cu and its group
121
How can I find the percent compositions of different isotopes when only given the atomic weight?
Set up the following equations:
X + Y = 1 (where X and Y represent percentages)
mass.X + mass.Y = atomic weight
Then substitute 1 in 2
122
What is Planck's relation? What does it represent?
```
E = h.f
h = Planck's constant = 6.6 x 10^-34 J.s
f = frequency of radiation
```
E is the energy emitted from matter
123
What is the equation for the angular momentum of an orbiting electron?
L = n.h / 2pi
n = principal quantum number
124
How to calculate the energy of 1 electron?
E = - Rh/n^2
Rh= Rydberg unit of energy = 2.2 x 10 ^-18 J/e-
125
How to calculate the electromagnetic energy of an emitted photon?
E = h.c/lambda
126
How to calculated the energy associated with a change in principal quantum number?
E = -Rh . [1/ni^2 - 1/nf^2]
127
What is the maximum number of electrons in a shell?
2n^2
128
What is the maximum number of electrons in a subshell?
4 l + 2
129
What is Hund's rule?
Electrons fill empty orbitals first before doubling up
130
What is the Heisenberg uncertainty principle?
Refers to the inability to know the momentum and position of a single electron simulatenously
131
What is the Bohr model?
Early attempt to describe the behavior of the single electron in the hydrogen atom
132
What is the Rutherford model?
Described a dense, positively charged nucleus
133
What are the possible values for l (quantum number)
0 - (n-1)
134
What are the possible values for ml (quantum number)?
-l, 0, and +l
135
What is necessary for a molecule to appear on a UV spectrum? How does it affect the wavelength absorbed?
Molecule must have a small enough energy difference between its highest occupied molecular orbital (HOMO) and its lowest unoccupied molecular orbital (LUMO)
The smaller the difference the higher the wavelength absorbed
136
What is the equivalence point equation?
Na.Va = Nb.Vb
137
What is normality equal to?
Molarity . n
| n=number of protons, ions, electrons
138
Titrations in general: what determines the number of equivalence points?
depends on number of ionizable groups
139
What is the equation for gram equivalent weight?
Molar mass / n
140
What is the equation for equivalents?
Mass of compound / GEW
141
When calculating W as the area under the Pressure/Volume curve, how do you convert the area to Joules?
1 J = 1000 Pa.L
142
What is a malonic ester? In what reaction is one used?
Esters formed from propanedioic acid
| In the Gabriel synthesis
143
How to calculate the percentage of object being submerged in water?
object density / fluid density x100
144
What is the specific heat of water?
4.2 J/g.degree
145
How to calculate the spring constant from the restoring force?
k = F/x = mg/x
146
What does it mean for a molecule to be visible?
It has a high degree of conjugation
147
What primarily determines a molecule's reactivity?
number of valence electrons
148
What is an alkoxide ion?
Conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom
149
What is the equation to calculate the formal charge of an element?
fc = V - Nnonbonding - 1/2 Nbonding
```
V = valence electrons
Nnonbonding = # of non bonding electrons
```
150
What kind of amino acids are not ideal for alpha helices?
1. Amino acids that branch at the beta C: valine, isoleucine, threonine
2. Amino acids with R groups that can H-bond and are unbranched at beta C: have OH or NH bonds: serine
3. Amino acid that is too rigid/large: proline, tryptophan, phenylalanine, tyrosine
4. Amino acid that is too conformationally flexible: glycine
151
What kind of amino acids are ideal for beta sheets?
1. Large amino acids: tryptophan, phenylalanine, tyrosine
2. beta branched amino acids: valine, isoleucine, threonine
3. At the end of beta sheets: proline
152
What amino acids are ideal for alpha helices?
Methionine, alanine, leucine uncharged, glutamine, and lysine ("MALEK" in the amino-acid 1-letter codes)
153
What holds lipids together?
london dispersion forces + van der waals
154
What is the difference between London dispersion and Van der Waals forces?
London dispersion forces are the weakest VDW forces
155
What are London dispersion forces?
Arise due to dipoles
156
What are Van der Waals forces?
Includes all forces that act between 2 neutral molecules
157
What are disulfide links disrupted by (3)? Through what reaction?
1. 2-mercaptoethanol
2. Dithiothreitol
3. TCEP
Reduction
158
What does chaotropic agent mean?
Molecule in water solution that can disrupt H-bonds
159
What happens during alkene halogenation?
1. Pi bond attack one of the halogens --> forms a cyclic halonium ion
2. The second halogen needs to attack on the other side of the ring
3. It can attack at either C: racemic mixture of dihalides in anti fashion (not on the same side)
160
Which are stronger: short or long H bonds?
Short!
161
What is a chelating agent?
A substance whose molecules can form several bonds to a single metal ion.
162
What should I do when trying to determine the strongest dipole moment?
Draw them! These are vectors, so add them.
163
What is the rate order of a reaction?
The sum of all of the integers in the rate law
164
How to determine which reaction will happen the fastest?
It'll be the one with the lowest activation energy
165
What is the unit of the reaction rate?
Mol/L.sec
166
How to convert g/cm^3 to g/L?
Multiply by 1000
167
What are complex ion formations used for?
1. Used by protein active sites
| 2. Used to sequester toxic metals
168
How can you increase the solubility of solids?
Increase temperature
169
How can you increase the solubility of a gas? 2 options
1. Decrease temperature
| 2. Decrease partial pressure of the gas
170
What is the boiling point of a very dilute solution?
373 K
171
When is pH = 7 = neutral valid?
At 25 C
172
What is the formula for ammonium?
NH4+
173
What is the formula for phosphoric acid?
H3PO4
174
What does a very negative pKa mean?
Very strong acid
175
How do pKa and pKb relate?
pKa = 14 - pKb
176
How do Ka and Kb relate?
Ka = 10^-14 / Kb
177
Where is the pKa1 on a titration curve?
midway between starting point and equivalence point
178
Where is the pKa2 on a titration curve?
midway between first and second equivalence point
179
What does high Ka mean?
Strong acid
180
When asked which is the weakest base...??
Look for the strongest acid!
181
What do indicators need?
A pKa close to the pH at the endpoint of the titration
182
What is the formula of the sulfate ion?
SO4 2-
183
What does Pd/C do?
Catalyzes the addition of hydrogen to C–C multiple bonds → if they are “partially” reacted with it, then some double bonds will be left!
184
What are buffers?
Weak acid and conjugate base → neutralize each other because the dissociation never goes to completion
185
How can I assess if an H is acidic?
If the negative charge left behind can be stabilized in some fashion then it’s acidic.
186
What is the difference between the conjugate base of a weak acid and that of a strong acid?
Weak acid → weak base
| Strong acid → VERY weak base
187
What happens when you add an amine to a ketone?
Imine
188
What is another word for transition state?
Activated complex
189
What is another word for bomb calorimeter?
Decomposition vessel
190
What is another word for bond dissociation energy ?
Bond enthalpy
191
What is the formula for acetylene?
C2H2
192
What is the standard equation for a combustion reaction?
compound + O2 --> H2O + CO2
193
What is a Bronsted Lowry base?
Can accept protons
194
What is a Lewis base?
Can donate electron pairs
195
What is an Arrhenius base?
Can dissociate to produce an excess of hydroxide ions in solution
196
What is the equation for the definition of rate?
Rate = - Delta [A]/a.Delta t = - Delta [B] / b.Delta t
197
What is the equation for the collision theory?
Rate = Z x f
Z=number of collisions
f=fraction of successful colliisions
198
What is another word for dissolution?
Solvation
199
What does it mean when "quinone" is included in the name of a molecule?
Contains an aromatic ring
200
What happens during a double-displacement reaction? What is another name for it?
Elements from 2 different compounds swap places
| Metathesis
201
What is a neutralization reaction?
Specific type of double-displacement reaction in which an acid reacts with a base to produce a salt and water
202
What is a disproportionation reaction? What is another name for it?
Specific type of redox where an element undergoes both reduction and oxidation in the products
Also called a dismutation reaction
203
What is the frequency factor of a reaction? What is another name for it?
Measure of how often molecules in a certain reaction collide
Also called attempt frequency
204
What is another name for complex ion?
Coordination compound
205
How do I calculate Delta G off of a reaction profile graph?
Difference in energy of products and reactants
206
How do I calculate the original pH of a solution (before titration)?
1. Figure out Ka
2. Set up: Ka = x^2/([HA] - x)
3. Solve for x = [H+]
207
How to know how much volume will be needed to reach the half equivalence point?
Divide volume needed for the equivalence point by 2
208
How do I compare acidity strength between molecules that only differ in the sp hybridization of the anion?
sp3
209
How to determine whether a molecule is sp3, sp2, or sp?
Look at how many areas of electron density there are around it
210
What are exceptions where O has not a -2 oxidation number?
O2 (0), H2O2 (-1)
211
What does cholesterol look like?
Fused 4 carbon rings: three 6 C rings + one 5 C ring
212
What is the structure for steroid hormones?
Fused 4 carbon rings (sometimes 5)
213
What are the pKas of the C and N groups on amino acids?
2 and 9
214
What amino acid is ideal for the "joints" between a-helixes?
Glycine
215
If neither reactant is chiral, but the product is, how did this happen?
The enzyme is chiral!
216
How to balance a redox reaction in basic solutions?
1. First assume it is acidic
2. If that is not one of the answer choices, replace all of the H+ with water and add the same number of OH- on the other side
3. Cancel out the H2O molecules (sometimes)
217
What are the products of aldehyde + catalytic base?
Aldol
218
What is the product of aldehyde + catalytic base + heat?
Aldol condensation
219
When trying to assign oxidation numbers to an element in a molecule that is not uniformly oxidized, what should I do?
Just look at formula overall
220
How to increase the solubility of solids? Why?
Increase temperature
| Dissolution is endothermic
221
How to increase the solubility of gases?
Decrease temperature or increase the partial pressure of the gas above the solvent
222
What is the difference between compounds and molecules?
All molecules are compounds, but not all compounds are molecules. An example of a compound that is NOT a molecule would be an ionic salt. Sodium chloride, for example, has a unique ratio of elements in it (as is true for all compounds), but there is no such thing as a NaCl “molecule.”
