OC DAT BOOTCAMP Missed Tests Questions Flashcards
bronsted-lowry base
proton acceptor
bronsted-lowry acid
proton donor
meso compound
must have at least 2 chiral centers and a plane symmetry
thin layer chromatography (TLC)
most soluble compound travels the farthest and furthest up the plate
TLC plate is coated with a polar substance ( silica gel ) and the developing solvent ( hexane ) is nonpolar:
the greater the distance a compound travels, the more nonpolar it is and the greater its Rf value
the shorter the distance a compound travels, the more polar it is and the lower its Rf value
In TLC, the more nonpolar a compound is, the
greater its Rf value
In TLC, the more polar a compound, the
lower its Rf value
CARDIO
CHARGE
ATOM
RESONANCE
DIPOLE INDUCTION
ORBITALS
heterogenous mixtures can be separated by
filtration
homogenous mixtures can be separated by
distillation and gas chromatography
filtration
a laboratory technique used to separate a solid from a liquid
filterable mixtures must consist of a
solid precipitate surrounded by a liquid solvent
therefore they are categorized as heterogenous mixture, not homogenous ones
fractional distillation
uses differences in boiling points to separate two or more intermixed substances that form a homogenous solution
used when boiling points are very close to each other ( 25 difference )
simple distillation
used when the boiling points are vastly different from each other ( >25 difference)
gas chromatography
used to separate a homogenous solution of 2 or more liquid substances that can be converted to gases
separation is based on differences in boiling point
staggered anti
most stable
staggered gauche
eclipsed
least stable
define staggered
all groups are spaced out as far as possible
define anti
two bulkiest substituents (methyls) are 180 degrees from each other, meaning that the conformation is anti
the staggered anti conformation is _________ than the staggered gauche and eclipsed conformations
more stable
enantiomers
non-superimposable mirror images
opposite configurations at each chiral center
mechanistic steps of radical bromination
- Initiation
- radicals on right side of equation - Propagation
- has one or more radicals on both sides of the equation - Termination
- radicals on the left side of equation
electron withdrawers ( meta directors )
electron donors ( ortho/para )
the acidity of a compound increases as the atom that the acidic hydrogen is bound to
increases in size
constitutional isomers
branching increases
melting point
branching decreases
the boiling point
reactivity
hemiacetal
hemiketal
column chromatography
separates compounds based on polarity
since silica gel has a polar surface, it interacts more with polar molecules
polar molecules stick to the column and take longer to elute
organic solvents are nonpolar, the most nonpolar compound dissolves the best in the eluent and travels fastest through the column
which lab technique produces a fingerprint region?
infrared spectroscopy
600-1400 cm -1
z isomer
e isomer
more stable than the corresponding Z isomers
stability of alkene depends on steric bulk
E isomers have bulkier groups pointing in opposite directions
E isomers are generally more stable than the corresponding Z isomers
degrees of unsaturation
C-(H/2)-(X/2)+(N/2)+1
acyl carbon
where nucleophilic substitution takes place
alpha carbons
one carbon away from carbonyl
beta carbons
gamma carbons
decreasing boiling point
In order of decreasing strength of intermolecular forces:
hydrogen bonding > dipole-dipole > dispersion forces.
increasing carbocation stability
In order of decreasing carbocation stability: 3° > 2° > 1° > methyl.
carbocations will rearrange via
1,2-methyl shift
1,2-hydride shift
ring shift
to achieve a more stable formation
each C=C bond includes one sigma bond and one pi bond
each carbon atom forms its sigma bond by overlapping one its sp2 orbitals . in other words, the sigma bond is made by sp2-sp2 overlap
the carbon atoms form the pi bond by overlapping their leftover p orbitals. In other words, the pi bond is maed by p-p overlap
Trend of Amino Acid Functional Groups
If the pKa of the functional group is less than the pH of the solution, then the functional group will be deprotonated.
If the pKa of the functional group is greater than the pH of the solution, then the functional group will be protonated.
gas liquid chromatography
A mixture of compounds is injected into a gas chromatograph.
The gas chromatograph heats the mixture of compounds until they boil, and then pushes them using a gas (e.g. helium) down a coiled tube.
The individual components in the mixture separate by boiling point, with the lowest-boiling-point component coming off the fastest.
extraction
Extraction separates solid or liquid compounds based on solubility and acid/base properties.
Extraction would present difficulty in separating volatile compounds because the volatiles would likely boil off while attempting to evaporate eluent or extraction solvents
Index of hydrogen deficiency (or degrees of unsaturation) of a compound =
rings + # pi bonds
Only LiAlH4 can reduce
esters and carboxylic acids
NaBH4 and LiAlH4 can reduce
aldehydes
ketones
acid chlorides
acid anhydrides
functional groups that react with a nucleophile
aldehydes
ketones
alkyl halides
alkanes
epoxides
Keto-enol tautomerization
describes how ketones and aldehydes exist in rapid equilibrium with a tautomeric form known as an enol. Tautomers are constitutional isomers that interconvert in rapid equilibrium.
The chemical equilibrium of keto-enol tautomerization usually strongly favors the keto-form over the enol-form. We denote the preference for the keto-form using special arrows, as shown below.
bond length is related to
atom size and effective orbital overlap
This means that bond lengths increase going down and to the left on the periodic table.
SN1 and E1 reactions prefer
polar protic solvents
SN2 and E2 reactions prefer
polar aprotic solvents
protic solvents
have H atoms bonded to O,N,S
CH3OH
CH3CH2OH
CH3COOH
H2O
polar aprotic solvents
DMSO
Acetone
DMF
THF
either
The radical halogenation reaction below proceeds through a radical intermediate.
increasing reactivity
Which of the following would proceed in a one step reaction?
SN2 and E2 reactions occur in one step.
SN2 and E2 reactions use strong nucleophiles/bases.
Thus, the reaction proceeds in one step－the strong nucleophile/base is able to attack and the leaving group leaves simultaneously.
SN1 and E1 reactions occur in two step due to the formation of a carbocation.
SN1 and E1 reactions use weak nucleophiles/bases. Thus, the reaction proceeds in two steps－the leaving group must exit before the nucleophile/base is able to attack.
the order for IUPAC naming
Carboxylic acid (RCO2H)
Acid anhydride
Ester (RCO2R’)
Acid halide (RCOCl)
Amide [R’C(O)NR2]
Nitrile
Aldehyde
Ketone
Alcohol (ROH)
Phenol (PhOH)
Amine (R’-NR2)
Alkene
Alkyne
Ether (R’OR)
Alkyl halide (RX)
Nitro (NO2)
Which wavelength of light is used to induce vibrational transitions?
Infrared
Nitration of toluene (Ph-CH3) with HNO3/H2SO4 produces
Nitration (HNO3/H2SO4) adds NO2 to aromatic compounds.
Because methyl groups are ortho/para directors, NO2 will be added to the ortho and para positions. The para position is preferred over the ortho position because it creates less steric hindrance.
In addition, methyl groups are electron donors. CH3 causes toluene to be more reactive/activated than benzene, thereby resulting in faster electrophilic aromatic substitution (EAS) reactions. Choice [A] is the answer.
Electron-donating groups (e.g. CH3) are
ortho/para directors, and these substituents will cause EAS reactions to occur faster.
Electron-withdrawing groups (e.g. NO2) are meta directors,
these substituents will cause EAS reactions to occur slower.
Electron-donating groups (e.g. CH3) are ortho/para directors,
these substituents will cause EAS reactions to occur faster.
For a molecule to exhibit optical activity, it must have
a chiral center
Aldol condensation combines two
carbonyl compounds to form a new B-hydroxy carbonyl
further condensation forms an a,b-unsaturated carbonyl
First, in order to participate in aldol condensation, the starting carbonyl must have an α-hydrogen, which is a hydrogen bonded to a carbon that is immediately adjacent to a carbonyl carbon.
The less steric hindrance, the more reactive the molecule. Therefore, aldehydes are more reactive than ketones.
what is the rate law for the following rxn?
Rate = k [electrophile][nucleophile]
Rate = k [CH3CH2CHBrCH3][OH-]
The nucleophile (OH-) in the reaction below is strong, which suggests that we are dealing with an SN2 reaction.
This means that the rate at which the reaction occurs depends on the concentrations of both the electrophile and the nucleophile (i.e. the rate is bimolecular).
Acid-catalyzed hydrolysis of an acetal results in the following products:
Two equivalents of alcohol (if the acetal is acyclic)
Diol (if the acetal is cyclic)
Carbonyl species
Something that can act as either a base or an acid is called
amphoteric
The energy content of the transition state of a chemical reaction
is greater than both reactants and products
‡ is the transition state (highest energy point in the reaction).
Ea is the activation energy (distance from reactants to the top of the transition state).
ΔH is the change in enthalpy between the reactants and products. We are looking at an endothermic reaction because the products are at a higher energy than the reactants (products - reactants = +∆H).
Which best describes the regioselectivity and stereospecificity in the oxymercuration-demercuration of an alkene?
markovinikov orientation with anti-addition
pericyclic addition
The reaction below is a Diels-Alder reaction.
Diels-Alder reactions proceed through pericyclic addition. This is characterized by electrons forming bonds in a circular manner, resulting in a cyclic structure. It is an addition reaction, as two reactants join to form one product.
Which of the following is a byproduct from reacting a carboxylic acid with an amine in the presence of heat?
H2O
Which of the following would proceed the slowest in an electrophilic aromatic substitution?
The reactivity of an aromatic compound is determined by its substituents. More reactive compounds will undergo EAS faster, and less reactive compounds will undergo EAS slower.
Electron withdrawing groups are substituents that draw electron density out of the aromatic pi-system, thereby decreasing the reactivity of the benzene, and directing the addition of new substituents to the meta position.
To identify the aromatic compound that will undergo EAS the slowest, we must find the substituent that is an electron withdrawer (deactivates the ring).
All of the following functional groups can be present in C8H16BrClO EXCEPT for one. Which one is the EXCEPTION?
Because our compound has zero degrees of unsaturation, it cannot contain any double bonds or rings. A ketone functional group includes a double bond, and therefore cannot be present in our compound.
What is the relationship between the following pair of structures?
The isomers below have opposite R,S configurations, making them enantiomers.
Butyric acid undergoing reaction with lithium aluminum hydride (LiAlH4) and acid workup afterwards yields which of the following?
butan-1-ol
Which of the following compounds could be separated by acid-base extraction?
two compounds in a mixture can be separated by acid-base extraction if one compound is acidic, and the other is basic.
Acid-base extractions only work when one of the compounds responds to a treatment, but the other does not. If both compounds respond to the same treatment, then they will both be pulled into the aqueous layer.
Therefore, we are looking for one acidic compound (e.g. carboxylic acids or phenols), and one basic compound (e.g. amines).
The diagram below plots the energy of the reaction between 1,3-butadiene and HBr at two different temperatures. Which of the following conclusions is correct?
the solid line plots the energy of the thermodynamic product and will be the major product at higher temperatures
The dashed line plots the energy of the kinetic product and will be the major product at lower temperatures.
The dashed line has a lower Ea because it forms the more stable, secondary carbocation intermediate.
It also has a higher final energy because the product is the less stable, mono-substituted alkene.
Because the reaction has a lower Ea, it is more likely to occur at lower temperatures.
What is the major product of the following reaction?
Reaction of an alkene with HBr in the presence of CH3OOCH3 (peroxide) results in the anti-Markovnikov addition of H and Br. Since this reaction proceeds through a radical intermediate, rearrangement is not possible.
LiAlH4 reduces ketones down to which of the following functional groups?
secondary alcohols
What is the major product of the following reaction?
The Wittig reaction turns the C=O of an aldehyde or ketone into a C=C.
Polar aprotic solvents are favored for SN2 reactions. Examples include acetone, DMSO, acetonitrile, and DMF－they are polar enough to dissolve the substrate and nucleophile, but they do not participate in hydrogen bonding with the nucleophile (which would dampen its reactivity).
Polar protic solvents are the worst solvents for SN2 reactions;
they solvate the nucleophile so that it cannot attack. Polar protic solvents are capable of hydrogen bonding, i.e. they have hydrogens directly bonded to F, O, or N. Examples include water, ethanol, ammonia, acetic acid, and methanol.
Grignard reagents are basic compounds and will attack the
less substituted side of epoxides. This epoxide is symmetrical, so this does not make a difference in this reaction.
Which of the following reagents would convert 2-butanol to 2-butanone?
Which of the following molecules is the most nucleophilic?
Molecules that are stabilized by resonance are less inclined to behave like nucleophiles. A good nucleophile will have a concentrated, strong pair of electrons ready to donate. Resonance decreases this concentration, because the electron pair is more spread out through the molecule
Which of the following will undergo free radical bromination most rapidly?
Free radical bromination is a type of substitution reaction in which a hydrogen is replaced with a bromine. The free radical halogenation reaction mechanism passes through a radical intermediate. The formation of the radical intermediate is the rate determining step; thus, the speed of the reaction is determined by the stability of the radical intermediate.
The order of stability of alkyl radicals is: 3° > 2° > 1° > methyl.
Which of the following is true regarding the two structures shown below?
they have the same vapor pressure
Which of the following reagents would best accomplish the following transformation?
Stability of alkyl radicals is:
3° > 2° > 1° > methyl.
What is the major product of the following reaction?
In which of the following laboratory techniques would the density of the solvent matter?
extraction
Which molecule is most likely to dehydrate under normal conditions?
Dehydrations are chemical reactions that involve the removal of a water from a reactant molecule.
Under normal conditions, alcohols dehydrate and give rise to an alkene product via an E1 mechanism. The question asks which is most likely to dehydrate, which is the same as asking which molecule will dehydrate the fastest.
The rate dehydration occurs is dependent on the stability of the carbocation intermediate that forms during the reaction. The general trend of carbocation stability:
As electronegativity decreases,
the basicity increases.
How would doubling the concentration of both 2-chloro-3-methylbutane and CH3CH2O– affect the rate of the reaction below?
Secondary alkyl halide in the presence of strong base will undergo E2 reactions.
The rate law for an E2 reaction is rate = k[substrate][base].
Which of the following functional groups is most easily oxidized?
aldehyde
aldehyde
nitrile
carboxylic acid
1 alkyl halide
ester
s character percentage of s and p
100% s
0% p
sp character percentage of s and p
50% s
50% p
sp2 character percentage s and p
33% s
66% p
sp3 character percentage sp and p
25% s
75% p
