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