Organic Chemistry Lab final
what are two ways that the extraction efficiency could be maximized to get the most trimyristin out of the nutmeg?
-repeat extraction more times -use more ether -stir longer
IR spectroscopy enables us to determine functional groups based on
bond stretching and bending energies
how can purification be obtained through distillation?
by collecting multiple fractions as the distillation temperature approached the boiling point of the substance
IR range of 2500-3100, sharp
carboxylic acid
alkyl halides are not soluble in water even though they are somewhat polar because they cannot participate in what?
hydrogen bonding
Which test provides the most information about functional groups?
infrared spectroscopy
What does two spots on a TLC plate indicate?
Either that a reaction is taking place, or impurity in the product
Why was N-Phenylmalemide used as the dienophile in our Diels-Alder reaction?
-it has electron withdrawing groups and is therefore more reactive -it will add a UV-chromophore to the product so that the reaction can be followed by TLC
indication of aromatic compounds on IRs
1600, 1580, 1500, and 1450 cm-1. have sharp bands and variable intensity
o-disubstitution of aromatic compounds IR
770-735 cm-1
p-disubstituion of aromatic compounds IR
800-860 cm-1
m-disubstitution of aromatic compound IR
860-900, 760-810, 670-710
what is the chemical formula of the heavy white precipitate that forms when ethanoic solver nitrate is added to a solution of 1-bromoethylbenzene?
AgBr
What would happen if the rate of the addition of alkyl bromide to the reaction medium got out of control?
Another side reaction could have occurred. This reaction is the coupling reaction between the organomagnesium halide and the alkyl halide. (R-R, MgX2)
Which compound is more polar? Something that dissolves in... A. ether, but not water B. water, but not ether C. both ether and water
B
In the Grignard reaction, what was used to help initiate the reaction and activate the magnesium surface?
Iodine
what type of extraction was done to isolate trimyristin from nutmeg?
solid-liquid
how are Mw and Mn different?
Mw is the "average" Mn is the average assuming that each individual is weighted equally
what indicates that a compound is polydispersed?
Mw/Mn= more than 1
extraction separates compounds on the basis of their
solubility
Reactivity of organic halides with magnesium order
R-I > R-Br > R-Cl
What was the silver nitrate test?
Tested to see if 1-bromoethylbenzene was formed. If it was, a white precipitate was formed.
What role did Quinnoline play in the styrene formation?
Was the solvent. Drove the dehydrohalogenation of 1-bromoethylbenzene.
What functional group is in myristic acid and is protonated with the addition of HCl?
acid
What kind of reaction is the grignard reaction?
addition. Grignard reagents undergo rapid nucleophillic addition to the carbonyl group go aldehydes, ketones, carbon dioxide, and carboxylic acid derivatives.
IR frequency range of 3100-3650, wide
alcohol
IR range of 1000-1300
alcohol, ether, ester
IR range of 2850-3000
alkane, sp3
IR range of 1620-1680
alkene C=C
IR range of 3000-3100
alkene, sp2
what class of compounds will NOT dissolve/react with H2SO4? amines alcohols aldehydes alkenes alkyl halides ketones
alkyl halides
IR range of 2100-2260
alkyne, C---C
IR range of 3270-3320
alkyne, sp
if you were to mistakenly run your TLC plate with hexane as 100% eluent, rather than the ethyl acetate/ hexane mixture,
all of your compounds would move much less or not at all on the TLC plate
What role did AIBN play in that allowed the polymerization of sytrene to occur?
allows radical polymerization to occur
What is the significance of GPC?
also called size exclusion chromatography. is a type of liquid chromatography that separates polymers of different sizes. -larger compound eluted first -smaller compounds eluted second
IR range of 3300-3500, sharp
amine (N-H)
During the second step of the grignard reaction, why was it necessary to add the aldehyde solution to the grignard solution slowly?
because it's an exothermic reaction
why was n-phenylmalemide used as the dieneophile in the dies-alder reaction?
conjugated, and electron withdrawing groups
which has the lowest boiling point? nutmeg trimyristin diethyl ether methanol
diethyl ether
How is styrene made from 1-bromoethylbenzene?
elimination (E2) and dehydrohalogenation
IR spectroscopy allows us to determine the functional groups baed on
energies of bond stretching and bending vibrations
What functional group is present in trimyristin and is hydrolyzed with NaOH?
ester
Was Trimyristin more soluble in ether or methanol, and why?
ether, because it has lower polarity
What substance would be more likely to float on water, 1-bromoethylbenzene or ethylbenzene?
ethylbenzene, because it has a lower molecular weight.
Was the Grignard Reaction endothermic or exothermic?
exothermic
true or false, materials that do not contain covalent bonds are absorbed in IR
false
When compounds of similar structure have infrared spectra similar in the diagnostic region, what should be examined to tell the difference between the two?
fingerprint region
Which test provides the most information about substance purity?
gas chromatography
Organomagnesium halide that is formed in the presence of water
is consumed ina rapid acid-base reaction with water to form the corresponding hydrocarbon.
What about a melting point would indicate that a substance is impure?
it broadens and lowers
Why did all the water need to be isolated from the grignard product? How is this accomplished?
it interferes with distillation of the product. -A drying agent combines with water to form a hydrated inorganic compound
IR range of 1620-1800
ketone, aldehyde, carboxylic acid
AlCl3 is a bronsted acid bronsted base lewis acid lewis base
lewis acid
what is the advantage of using a cyclic diene rather than an acyclic one int he dies-alder reaction?
locked in the s-cis conformation
In GC, list how compounds will elute based on their boiling point starting from the shortest retention time going to the longest
lowest BP to highest BP
why was it not useful to recrystallize polystyrene?
many polymers are not crystalline materials
what IR frequencies might you see in 1-bromoethylbenzne?
medium and sharp at 3020 cm-1 medium and sharp at 2970 cm-1
Why weren't there any reactions listed for part I of the Trimyristin lab?
no chemical reactions took place. the trimyristin originally in the nutmeg was isolated and purified, but does not change chemical structure.
why won't a 100% yield of trimyristin be obtained?
nutmeg has many more elements than just trimyristin
thin layer chromatography separates compounds primarily on the basis of
polarity
What are the pros and cons of using magnesium sulfate as a drying agent?
pros: magnesium sulfate is generally more efficient at removing water than sodium sulfate is con: magnesium sulfate is sometimes hard to filter because it is a fine powder
When 1-bromoethylbenzene was made from ethylbenzene, what kind of a reaction was this?
radical substitution
fingerprint region
region below 1400 cm-1
after the second step in the grignard reaction, why is it necessary to workup the reaction with aqueous sodium bicarbonate?
so that alkenes are not formed during distillation
Why are ethers good solvents for the formation of Grignard reaction products?
strongly coordinate to the magnesium in organomegnesium halides
Friedel-Crafs alkylation is what type of a reaction?
substitution
Ceric Ammonium Nitrate test
tests for alcohols. positive test is indicated by a change in color of the reagent from yellow to orange-red when a few drops of the unknown are added.
2,4-Dinitrophenylhydrazine test
tests for aldehydes and ketones. (confirms presence of carbonyl groups) a positive test is the formation of a significant amount of the yellow to orange-red precipitate
Potassium Permanganate test (KMnO4)
tests for alkenes. A positive test is when the purple color fades, and a brown insoluble precipitate forms
what is the advantage of the reactants being less volatile than the solvent used for a chemical reaction?
the boiling point of the solvent restricts the temperature range that can be used when heating a reaction solution
How does one tell the polarity of a substance based on a TLC plate?
the closer it is to the bottom, the more polar it is
why are non-nucleophilic bases such as quinoline useful?
they prevent the corresponding substitution reaction from occurring where the base would substitute for the halogen
Why was the final ether solution treated with solid magnesium sulfate?
to dry the solution
What does it mean to reflux a solution
to heat a solution at a constant temperature
why did we add methanol to our concentrated ether solution of trimyristin?
to precipitate the trimyristin
True or false, at lower concentrations of the alkyl halide in the grignard reaction, the reaction of the alkyl halide with the magnesium metal is favored over the coupling reaction with the ether-soluble organomagnesium halide?
true
What would more rapid heating of the liquid rising in the condenser cause?
vapor to potentially escape out of the condenser, resulting in a partial loss of product, because those vapors would originally condense back to water if they flowed through the condenser with cold water
distillation separates compounds on the basis of their
volatility (bp)
