Organic chem Flashcards
what is another word for carbocation? and what is tis hybrid?
carbonium ; sp2
electron withdrawing vs electron donating
withdrawing are pulling electrons toward them
do nucleophiles like electrons
they have so many electrons that they give electrons away because they want to get closer to the nucleus so carry neg charge to let the e- seekers know
why is an oil bath used for the distillation method
helps to keep the constant temp bc oil will not evaporate
what keeps the condenser cool for the distillation
the movement of water in and out which is good since distillation undergoes vaporization and condensation
why do u need a vaccum in a distillation?
if u have compounds with high bp, u can uses the vacuum to lower the pressure which will hep to chang it to a gas
why is an oil hot bath and an ice bath needed for distillation?
so that molecules can go from gas to liquid (vice versa) quickly
what happens to temp during a phase change?
its constant
why use fractional distiilation?
when u distill again so that u can have an ideal compund purification from compounds with similar boiling points
which layer (organic or aqueous) has a higher density
the aqueaous phase (it contains ions and water)
organic layer has neutral compounds
during extractions what happens during the layers
u want the aqueous layer to come through to the flask and the organic layer to stay in the funnel.
this is used for separation so it is a purification method
Separate. By compound properties like ionic or nonpolar or by acid or base
So if u want to separate steroid VS nacl u will add ether and the steroid will dissolve in the ether and the more dense (water and ions) will be poured out first so basically polar goes out first because most dense due to water…
If u want a nonpolar, get a polar solvent
So use opp solvents of the desired compound
But for acid and base u will have rxn
The base will react well with acidic solvent and will travel down along with solvent to aqueous rxn to come out
Desired acid will need an a basic solvent
Neutral will stay in ether
what type of acid is a phenol
weak
acidity increases with what?
the more pos charge, electroneg (depends b/c have to remember atoms that are most acidic are the ones that are closer to the A of the periodic trend) and the bigger the atom
pick the one thatis most acidic
ammonia or ammonium
HI or HCL
ammonium
HI
the basic compounds have a what charge ?
neg
-log of 10?
-1
diff btwn pka and ph calcul
pka is log but ph (h+) is -log
order of acidity
- electroneg (halogens)
- carboxylic acids
- phenols (weak acid)
- carbonyls
- carbanions
whats the main diff btwn nucleophiles and elctrophiles
electrophiles are hungry for electrons (so carry the pos charges) so then the nucleophiles will be looking to give away electrons to them (they want to feed them) which will help them too because they want to be closer to the nucleus.
what makes better leaving groups
- stabilized molecules
- resonance
- halogens
- water or other neutral compounds
which one is more stable (thermodynamic) … enol or ketol
ketol
what does the reagent H2/ Ni do ?
it removes the ring strain of ONLY cyclopropane and cyclo butane and makes them a regular non ring alkane
conformational isomer
same molecular formula but differ by rotation around a sigma bond
staggered vs gauche
syn vs anti conformers
staggered is less crowded and more stable due to electron repulsion
syn is that the big groups are next to each other while anti means that they are across
epitope
contains the virus identity but can go overlooked by immune system if it has an envelope
constitutional isomer
compounds with the same molecular formula but have atoms connected together differently
conformational isomers
compounds with same molec formula but can be a chair newman or fisher projection because they all are arranged differently around the sigma bond (rotations may be different as well)
another key word for enantiomers are
racemic
stereoisomerism
same meolc formula but differ with spatial arrangement of atoms like r/s config and e/z confog
factors a chirality
- asymmetric carbon
- not superimposable
formula for stereoisomers
2^n and n is number of chiral centers
unsaturation formula
[2n+2) - x] / 2
x is hydrogens
ignore oxy
halogens are 1
nitrogen = add 1 more carbon AND hydrogen
two things to focus on when r/s config?
if it has D (two hydroogens) or T(3 hydrogens) u should base priorty from heaviest to lightest atomic weight
usually it goes by atomic number but halogens and O always gets priority
halogens comes b4 oh group
what has the same physical properties? enantiomers or disastieromers
enenatiomers
describe the process of separating enantiomers
u have to use resolution to separate the enantiomers into diasteriomers which will give them diff properties like diff boiling points
use chiral probe that associates with the covalent bomds hydrogen bonds or salts
ex of geometric isomers
e/z
cis/ trans
ir frequency for sharp and intense carbonyl
ketone is 1700
1735-1680
wavenumber incr as what to freq
incr
o-h bond ir freq is
3650 - 3200
carbon double bond ir freq
1680 - 1620
for an nmr the # of sets of peaks tells
of nonequiv protons in the molecule
splitting patterns of the peaks tells
tells u # of equiv protons
ex: one peak means that all hydrog are equal
Paper chromatography
have a mixture and separating its components through polarity
mobile phase (organic solvent or even h20) liquid stationary phase (paper) solid
capillary action will cause the dye to travek from sample stop to a higher spot
if separated in more than one spot - more than one component
- one that travels more is attracted to solvent
- one that travels less is attracted to the stationary phase like the paper
thin layer chromatography
use glass that is made out of silica (polar stationary)
column chromoatog
dump more solvent and separate through diff bands that will travel down
More strongly attracted compound will travel slower than the weakly attracted compound
The one that elutes first is the one that does not attract. Well to the stationary phase so it will be mor on the lower bottom of system
Stationary is usually polar silica Or alumina
Agarose is polar used for electrophoresis
size exchange chromatog
stationary is beads that have wholes that have the tiny compounds that get stuck in there so the large ones travel faster
ion exchange chromatog
compounds with same charge will be repelled so to the stationary so they will travel faster but the ones with opp charge will be attracted to the charge so they will travel slowly
separates by charge
affinity chromotog
very specific interactions like an enzy,me and substrate
usually the binding of the substrate is bound and everything gets washed out
high performance/pressure chromotog (hplc)
workinh with smaller compounds and more sensitive
gas chromatog
gas is the mobile phase
stationary is liquid
most volatile (lower bp) travel faster than the higher bp
separates by boiling point
gel electrophoresis
separates molecules by size
useful for dna neg charge which will travel to pos charge
- restriction enzymes to break dna into fragaments
- longer dna fragments (more mw) closer to wells while shorter ones are closer to the pos charge (anode)
- overall will look like bands and compare the similarity
agarose
polysaccharide polymer lets dna molecules travel through it with holes that the dna travels into
cathode
has a neg charge because this is where reduction takes place
anode
has a pos charge bc this is where oxidation comes
dna ladder
standard of the base pairs to refer to for the gel electrophoresis
agarose vs sds page (polyacrimide)
agarose has big pores so used for big dna fragments (larger than 50 base pairs)
sds page is used for smaller thimgs and proteins
why do acetals and hemiacetals form
bc alcohol is the nucleophile
hemiacetal forms bc of weak nucleophiule and results with one carbon with one oh group and one OR group
acetal has 2 OR groups on same carbon and a good leaving group
ex of weak nucleophile
carbonyl by itself
what happens when the primary amine is the nucleophile
primary amine reacted with the carbonyl will make a imine
a primary amine only has 1 carbon attached to the nitrogen
two hydrogens need to be present like in NH2 and an imine will form which is the carbon double bond to the nitrogen
what happens when the secondary amine is the nucleophile
enamine is enol form of the two carbon with nitrogen attached to molecule as well
Primary secondary etc amines just mean how many carbons r attached to the nitrogen
Ex is secondary amines have 2 carbons attached
why are enamines and enols able to become nucleophiles
they are not stable forms and have an alpha hydrogen that is reactive and can attack
Enamines have double bond btwn carbon and nitrogen
nucleophilic enolate can react with what at what part?
can react with ketone or aldehyde and will attack from the enolate carbon but will go back to an aldol
When the enolate of an aldehyde or a ketone reacts at the α-carbon with the carbonyl of another molecule under basic or acidic conditions to obtain β-hydroxy aldehyde or ketone, this reaction is called Aldol Reaction.
Aldol addition has oh and carbonyl groups
Aldol condensation has no oh group bc it loses h20
heat elimates what
hydrogen and oxygen (water)
aldol has what two characteristics
alcohol and aldehyde
aldol vs retro aldol rxn vs aldol condensation
aldol makes bigger products and add things together
retro aldol makes smaller products and retro (maybe aldol too must check!) will break the bond at the alpha carbon of the carbonyl
aldol condensation uses heat to form a product that is an enal (aldehyde and enol) due to base attacking twice
saponification
use animal fat (base) to get addition, then elimination of the leaving group to get the soap
2 sigma bond to 1 pi bond
Breaking a fat like oil along with a base to form a type of glycerol and soap (sometimes can be a fatty acid or a carbon attached to a double bond oxygen, alkali metal, and another r group
trannsesterification
without a base you can have another ester instead of the one that u started with
true or false
an ester posessing two alpha hydrogens is required for beta ketoester formation to be driven to compeltion
true because it causes the base to act more as a base
why are oh groups bad for leaving groups?
not necessarily bad but the bases can steal the hydrogens because basic instead of an acid that will help the leaving group occur
h20 is a good leaving group
the one tghat has the l.g is the nucleophile
no
where is usually the addition cut when it comes to nucleophile attck
alpha beta bond must be cut …
its alpha next to cafrbonyl
claisian synthesis
The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone.
basically the oh disparears and rest of molecule reacts with the other one but the product should look VERY SIMILIAR to the reactant, just without the OH group
think of water disapearing
whe it comes to polarity of rf what can u tell
more polar is more slower and lower rf value
most polar groups that usually have small rf values
cooh
oh
nh3
when it comes to tlc, ether is ??
nonpolar so it will interact with polar molecules
nonreverse tlc means?
use polar coating as normal and the nonpolar will elute first
Reverse phase chromatography
Non polar coating like organic solvent which will cause the nonpolar to like the coating and want to join it so polar will elute first or travel farther
Enol VS enolate
Enol is double bonded carbon but with oh and r group attached to that carbon
Enolate double bonded carbon but with o negative and r group attached to that carbon
pyranose vs hexose
pyranose is a 6 membered ring but can be made of 6 diff atoms like oxygen so like 5 carbons and 1 oxygen
hexose is a d membered carbon sugar
main structural formula for ketone and aldehyde
ketone is like CO
aldehyde is CHO
how do u know the placement of oh and h groups on the fisher to the carbohydrate ring form?
downright upLEFTING
ex: everything on left will be up for glucose, only one OH at the third carbon on the left.. but has only one H at the third carbon on the roght side
tautomerization
uses an acid or base to go from keto to enol vice versa
base causes the alpha carbon next to carbonyl to get snatched by carbon to turn into enol form (or enolate form with an carbanion or oxyanion)
if acid, the carbonyl will get the h off f acid
alpha vs beta anomer
alpha has oh on bottom (fish shape so in the sea)
In the base catalyzed reaction, why doesn’t -OH do a nucleophilic attack the carbonyl carbon instead of the alpha hydrogen?
The hydrogens on the alpha carbon are more acidic, so OH is more likely to pull off that proton rather than go for a nucleophilic attack on the carbonyl carbon.
ethoxide and LDA have what in common?
both strong bases
why does the kinetic reaction need to take place in a cold environment? I would have assumed the “fast” kinetic product can be formed at room temperature, but the thermodynamic product would need the temperature control.
The kinetic product benefits from the colder temperature because it has a lower activation energy and the activation energy of the reverse reaction (products reforming the reactants) is to great for the reverse reaction to proceed. Once the kinetic reaction occurs, which is the faster of the two reactions, the kinetic products won’t be able to reform the reactants and possibly undergo a reaction forming the more stable thermodynamic product. Consequently, more of the reactants will be locked in to the kinetic product.
At higher temperatures the reaction will favor the more stable thermodynamic product because the reverse reaction can occur for the kinetic products and will have a lower activation energy than the reverse reaction for the thermodynamic products. Thus, kinetic products will be more likely to reform the reactants than thermodynamic products.
Consequently, the higher temperatures allow reversal of the reaction and the higher activation energy of the thermodynamic product will produce an even greater activation energy for the reverse reaction if the initial reaction is exothermic. Higher activation energies indicate less favorable reactions so the products are more locked in to the thermodynamic product.
What is the function of the enolate
It’s an excellent nucleophile. Look up “alpha carbon chemistry” for examples of the various reactions/roles of such nucleophiles (i.e. alkylation, aldol, etc.).
Why does hydride from NaH deprotonate the enolate, but hydride from LiAlH4 nucleophilically attack the back of the carbonyl to reduce it to the alcohol?
NaH is a strong base so it will deprotonate the carboxylic acid first. This makes the hydride ion lose/ decrease its nucleophilicity. LAH does not have problem with this so it will strongly reduce carboxylic acid and ester to alcohol. NaBH4 cannot reduce carboxylic acid because it is not reactive enough.
which sides of mol.ecules do kinetic and thermo attack
kinetic is hitting less substituted
thermo will go for more sterically hindered alpha carbon of carbonyl
gram equivalent weight of h2so4
take the molecular formula and then divide by the number of protrons so in this case will divide by 2
neutralization formula
acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water.
combination reaction
using both reactants to form a product
combustion rxn
o2 + gas = > h20 + co2
metathesis
two hydrocarbons react together to make two new hydrocarbons
decomposition
one reactant product breaks down into two or more products
steric #
(number of lone electron pairs on the central atom) + (number of atoms bonded to the central atom)
when adding h20 to aldehyde or ketone, what happens?
carbon attached to two oh , 1 h, and 1 r group if an aldehyde but would be two r groups of ketone
aka hydrate or germinal diol
when adding R-OH to an aldehyde or ketone, what happens?
carbon attached to two O-R groups, one R group, one H group if a ketone.
only one oh group if aldehyde
common catalysts to form the acetal
usually acidic (not talking about the reagent but the acetal) which could be h+, tluensulfonic acid TsOH R, H2SO4
what is the diff btwn diol and diothiol protection groups
diol puts protection group on carbonyl but the diothiol (SH) group protects the carboxylic acid from getting degraded to an oh by LIALH4
a secondary amine and a carbonyl reacting makes a what?
enamine which is a double bond between two carbons but one of the carbon are attached to a nitrogen
Grignard rxn
uses organometalics which are polar bonds between a metal and carbon, making the carbin very electroneg. also helps to cause the electroneg carbon to do a nucleophilic attack on the carbonyl
product will not show the metal but rather an oh group and the carbon group of the reactant
R-Li- X or R - Mg - X are the usual reactants that react with the carbonyl
r= carbon and the x= halogen
aldehyde + Grignard reactant =
have an extra carbon added to the molecule and overall will be a secondary alcohol
ketone + Grignard rxn =
no extra carbons so same number of carbons and overall molecule will be a tertiary alcohol
LiALH4 vs NaBH4 reducing agents
nabh4 is weaker nucleophile and can only reduce ketones and aldehydes into alcohols wherease the former can reduce all of them and then some like esters and carboxylic acids
tollen’s reagent for oxidizing rxns
which is a colorless, basic, aqueous solution containing silver ions coordinated to ammonia [Ag(NH3)2+]. It is prepared using a two-step procedure
ex: turns an aldehyde into an carboxylic acid
na2cr2o7, h2so4 vs tollen’s agent ([Ag(NH3)2+].
the former can oxidize aldehydes into carboxylic acids and alcohols into carbonyls
but the latter cannot oxidize alcohols
na2cr2o7 vs PCC
the former can oxidize alcohol into a carboxylic acid whereas the latter can oxidize alcohol to an aldehyde
Which of the following does NOT show optical activity?
A. (R)-2-butanol
B. (S)-2-butanol
C. A solution containing 1 M (R)-2-butanol and 2 M (S)-2-butanol
D. A solution containing 2 M (R)-2-butanol and 2 M (S)-2-butanol
Correct Answer: D
Explanation:
This is a racemic mixture of 2-butanol because it consists of equimolar amounts of (R)-2-butanol and (S)-2-butanol. The (R)-2-butanol molecule rotates the plane of polarized light in one direction, and the (S)-2-butanol rotates it by the same angle but in the opposite direction; as a result, no net rotation of polarized light is observed.
specific rotation
alpha = [alpha observed / c(l)]
c = molarity concentration l = length in deci m
Rank the following in order of decreasing leaving group ability: H2O, HO–, Br–, H–
Correct Answer: A
Explanation:
Good leaving groups are weak bases, which are the conjugates of strong acids. Leaving groups must also be stable once they leave the molecule. H2O is, by far, the most stable leaving group and will be extremely unreactive once it leaves the molecule through heterolysis. Br– is the conjugate base of HBr; HO– is the conjugate base of water. HBr is a much stronger acid than water, so Br– is a better leaving group than HO–. Finally, hydride (H–) is a very poor leaving group because it is extremely unstable in solution.
DiBal
reduction of esters to aldehyde
PCC
converts secondary alcohol to ketone
but not strong to turn primary alcohols or aldehyde into carboxylic acids
weak oxidizing agent
Which conversion between carboxylic acid derivatives is NOT possible by nucleophilic reaction?
Correct Answer: D
Explanation:
Remember, there is a hierarchy to the reactivity of carboxylic acid derivatives that dictates how reactive they are toward nucleophilic attack. In order from highest to lowest, this is anhydrides > carboxylic acids and esters > amides. In practical terms, this means that derivatives of higher reactivity can form derivatives of lower reactivity but not vice-versa. Nucleophilic attack of an ester cannot result in the corresponding anhydride because anhydrides are more reactive than esters.
