Chemical Chirality: Midterm
what is missing from a salicylic acid NMR?
a methyl peak
classes of chemical hazards: lachrymator
a substance that irritates the eyes and causes tears to flow
synthesis of aspirin: phosphoric acid
acid catalyst, protonates the acetic anhydride carbonyl
a proton on an electronegative atom is _______
acidic
polar molecule
can hydrogen bond (F, O, N)
Why do we wet the filter paper with a small amount of the solvent just before filtering our sample?
causes the paper to adhere to the plate and keeps materials from passing under the paper during filtration
most common source of injury in introductory labs
hot glass
why do ethanol and water mix
hydrogen bonding
why make new drugs
improve efficacy and eliminate side effects
organic compounds must be disposed...
in organic waste
percent conversion
integration of product/(integration of reagent + integration of product) x 100%
salicylic acid has some solubility in water. what would happen if you washed your crystals with too much water?
it will dissolve
Compounds can be protonated with an acid (like HCl) or deprotonated with a base (like NaOH) to move them to a different _____ (from organic to aqueous or vice versa).
layer
chronic toxicity
long-term exposure leads to problems
toxicity of ethanol
low dose: virtually no reaction extreme dose: mental impairment or death high, regular dose: cirrhosis, increased rate of aging, cancer,
classes of chemical hazards: flammable
low flash point
pka
lower pka = lower pH - most acidic proton will be removed - delocalization increases acidity - can explain: acidic proton, quality of leaving group, best NU, how to justify a mechanism
Synthesis of Salicylic Acid
methyl salicylate --1)NaOH 2)HCl --> salicylic acid + MeOH
will an ethanol water extraction work?
no, bc both are polar solvents and miscible
this reaction was formed NEAT (synthesis of aspirin) and water was added later. If you had performed the reaction in water (solvent), how would your results be different?
not as much aspirin would have formed because aspirin is soluble in water
synthesis of aspirin: Salicylic acid
nucleophilic phenol group
methyl salicylate
oil of wintergreen,
classes of chemical hazards: corrosive
oxidizer, strong acids and bases, cause chemical burns
why do you do the synthesis of aspirin in an erlenmeyer flask rather than a beaker?
prevents loss by evaporation or spilling
why do we use 3.0 equivalents of acetic anhydride
previous experimenters have optimized the reaction by using this amount
fastest possible reactions in organic chemistry
proton transfers
Salicylic acid + FeCl3 ->
purple -The phenol produces a complex with the iron atom to produce a deep purple color.
explain the observed solubility of quinizarin
quinizarin is non polar so it does not react with water
how do chemicals enter the body
shoes, clothing/aprons, safety goggles, gloves, eye wash fountain, safety showers surfaces = skin and eyes
neutral salt solutions can be disposed...
sink
erlenmeyer flask characteristics
sloped walls allow for swirling and stirring with minimal risk of spillage or solvent evaporation
longer wavelength = _____ HOMO LUMO gap
smaller
why is it important to clamp your filter flask even though it has a flat bottom?
so flask and vacuum do not move during filtration
MB
soluble in H2O - blue when O2 is present
calmagite
soluble in H2O and EtOH
acetic anhydride
solvent that drives the reaction of SA forward to form aspirin
How can I quickly find the molecular weights of my ozonolysis and reduction products?
subtract functional groups from the mass
why do we shake the sep funnel
the 2 liquids have increased surface area of contact and allows the separation of the liquids to be acquired quickly
LD50
the amount of a chemical that kills 50% of the animals in a test population
toxicity LD50
the dose required to kill 50% of mice, rats, etc.
theoretical yield
the maximum amount of product that can be produced from a given amount of reactant
flash point
the minimum temperature at which a liquid will spontaneously ignite
saponification
the reaction between a fat and a strong base to produce glycerol and the salt of a fatty acid (soap) - conversion of an ester to a carboxylic acid (Deprotonated) group
We can deduce that the extracted Compound B is contaminated with the extracted Compound A if....
there is a second peak in the UV-Vis spectroscopy
why is it important to dilute the entire extract layer to a known volume in a volumetric flask before doing additional dilutions?
to determine concentrations of the layer
why do we cool slowly
to encourage the formation of large, pure crystals.
why did we dry our products for a week
to make sure ALL the water is gone
why did we boil the water in the synthesis of aspirin
to make sure aspirin doesn't react with water to revert back to salicylic acid
ethyl acetate, ethanol, and ethyl ether are all in the ____ layer in extraction
top
I used ethyl acetate as my organic solvent. Is it top or bottom?
top! density of less than one
Water doesn't dissolve at low or high temperatures, ethanol dissolves at low and high temperatures. How do we get a good recrystallization solvent from this?
use a mixture, minimal amounts
1H NMR
used to determine the type and number of H atoms in a molecule
why do you want to remove the filtrate before pulling air over crystals
we need to remove the impurities in the solution before increasing pressure of the vacuum
Aspirin + FeCl3 ->
yellow - There is no complex that forms between the phenyl ester and the iron atom.
what would be affected if you did not carefully record how much your initial volumes were diluted by?
you can't find percent recovery
why did we add baking soda to the filtrate before throwing it away
you need to neutralize the HCl in the compound before throwing it down the sink otherwise it is v acidic
what is another problem with determining MP too quickly?
you will miss the range
acute hazards
(Immediate) may be ingested, inhaled, injected, or absorbed
filtrate of aspirin
(trace) methyl salicylate (trace) salicylic acid methanol (little) nacl & hcl
hazards in synthesis of salicylic acid
*methyl salicylate* - Corrosive! Toxic to blood, lungs, the nervous system and mucous membranes. Repeated exposure can cause organ damage! *sodium hydroxide* - Corrosive! Same reasons as above. *hydrochloric acid* - Corrosive! Strong acid!
beaker characteristics
- beakers can be hard to clamp - doesn't allow for even heating or cooling - has a high risk of spilling since the walls are not sloped
how to know you got pure SA
- colorless needles - melting pt of about 160 - FeCl3 turns purple - NMR
RBF characteristics
- good for uniform boiling or cooling - can easily be transferred to other apparatuses for different procedures - prevents spilling with rounded walls and a small opening
benzil
- insoluble in H2O, soluble in DCM - yellow
how would the melting point be affected if you determine MP before allowing the crystals to dry? how would % yield?
- it would melt at low temp and larger range bc of impurities - percent yield would inc bc water adds to actual yield
What gives off color
- more conjugation = easier to move e-s = more likely to give off a proton - absorption at UV & visible wavelengths: promotion of e- from HOMO to LUMO - extended conjugation reduces HOMO to LUMO gap - *observed color is complementary to the color absorbed*
why do you need more heat to bring the water to a boil than you need to maintain the solution boiling?
- need more energy to make water molecules gaseous, need to excite molecules to leave the liquid - less heat is needed to maintain the boiling
quinizarin
- soluble in hot H2O - orange/red brown
UV-Vis allows us to use __________ to tell us the concentration of our compound (and hence, how much was extracted).
Beer's law
classes of chemical hazards: reactive
Capable of readily undergoing a chemical change. explosions
synthesis of aspirin reaction
Conversion of a phenol group to a phenyl ester group.
percent yield
How did the reaction work out? How much product did we get compared to our starting material?
NMR spectroscopy
Hs are equivalent when there is free rotation or symmetry, each set of non-equivalent Hs give one NMR signal splitting pattern indicate number of Hs on adjacent carbons, subtract one multiplet for multiple splitting patterns integration indicates number of equivalent Hs represented by peak, can be a multiple of the number of Hs chemical shift is in ppm: 1. *EDG shifts right*/upfield/low ppm (alkyl groups) 2. *EWG shifts left*/downfield/high ppm (halogen, vinyl, aromatic, aldehyde, etc.)
synthesis of salicylic acid mechanism
1. add naoh - acid/base rxn first, then nucleophilic attack on C 2. add HCl
at what temperature will a solution of methyl salicylate and NaOH boil?
100
If skin or eyes come in contact with chemicals wash area with water for ?
15 minutes, eyelids open and no contacts
Typically, a λmax above _____ nm will tell us if a molecule is conjugated or not. More conjugated compounds can absorb longer wavelengths as they have a decreased HOMO-LUMO gap.
200
classes of chemical hazards: carcinogen
A cancer-causing substance
What constitutes a good recrystallization solvent?
A solvent in which your solute is insoluble at room temperature but soluble at high temperatures
extinction coefficient
Efficiency of absorbing optical energy (wavelength dependent) - can be deceiving since molecules with v high E can show almost no colors and affect your spectrometer
How can you determine acidity through pKa?
Low pKa molecules are more acidic; as you increase the pKa, you decrease acidity, hence increasing basicity.
Melting point
Lower bound: melting onset point (starts to liquify) Upper bound: completely melted point (fully liquid)
Why shouldn't you melt too quickly?
Lower, broader melting point
How well do the following organic solvents dissolve in water, and why? Methylene chloride Ethyl acetate Ethanol
MCL: Does not dissolve in water (nonpolar vs. polar) good for extraction EtOAC: Mild solubility in water (polar aprotic vs. polar protic) good for extraction EtOH: Completely soluble in water (polar protic vs. polar protic) not good for extraction
How much solvent should you use for recrystallization?
Minimal - to avoid dissolving too much product or oiling it out, making it impure.
which are good for carrying out reactions
RBF and Erlenmeyer Flask
NFP diamond ratings
RED = flashpoint (4 = ignitable, 0 = will not burn) BLUE = health hazard (4 = deadly, 0 = no health threat) YELLOW = reactivity (4 = may detonate, 0 = stable) WHITE = specific hazard (OX, ACID, CORR, etc.)
What purification technique was used for synthesis of SA?
Recrystallization- completely dissolving a boiling solvent and then allowing it to cool to form crystals.
What is thermometer lag?
The buffer time it takes for a thermometer to catch up with heating of something is heated too quickly.
Why is proper stirring important?
To ensure that we get all of the solid to dissolve! Many solids only dissolve with good stirring.
If we don't know what our compound is, ____________________ will tell us if it's conjugated or not.
UV spectroscopy
classes of chemical hazards: teratogen
any factor that can cause a birth defect
extraction separates what two types of compounds?
aqueous and organic
when calmagite, MB, Benzil, and Q are ionized, which layer do they appear in?
aqueous layer, will exist as a salt with whatever metal helped protonate or deprotonate it.
salicylic acid
bengay pain relief
DCM is in the _____ layer for extraction
bottom
is DCM top or bottom
bottom
make sure system is not ______ when setting up a reaction
closed
MSDS
computer generated, generalized hazard statements
corrosive compounds
concentrated solution of acids and bases
Color in compounds is caused by ________.
conjugation
saponification reaction
conversion from an ester group to a carboxylic acid ester - has a ch3 carboxylic acid - has H in place of CH3
appropriate clothing in a lab
covers midriff area and upper arms, closed toe shoes, gloves
what was the difference before and after crystallization of salicylic acid
crystal geometry stacks upon each other in a different way
The layers separating into their respective positions is based on what physical property?
density
fume hoods
designed as safety devices to transport vapors away from the laboratory in case of an emergency
FeCl3 test
detects the presence of phenol groups
what is the first step to turning off the vacuum
disconnect tubing - so crystals dont go into filtrate
what types of solvents are good for extraction
does not dissolve in water
how to increase percent yield of SA
dry more, allowed to cool more slowly
Synthesis of aspirin: acetic anhydride
electrophilic carbonyl carbon, carboxylate becomes a good leaving group
safety glasses
excellent impact protection, minimal splash protection
equivalent
experimental mole ratio we are using in a reaction - may NOT be the stoichiometric mole ratio
t/f: organic compounds can go down the sink
false
Extraction works best with multiple smaller washes rather than one large wash. Why?
fresher solvents, more surface area for reactions
how can you avoid thermometer lag?
heat solution slowly
