Lab Exam Final Flashcards
What are the correct steps for washing glassware
1- acetone
2- soap and water
3- acetone
How to dry glassware standard
on papertowel to air dry
How to dry glassware for moisture sensitive reactions
flame drying
first number pf taper glassware
diameter of top joint
second number of tapered glassware
inner length of the joint
weighing solids
weigh paper on scale, tare, add and remove solid till amount is reached
hot water baths
used for heating low boiling liquids
How to hold a pipette
vertically to prevent spilling and filling the bulb
How does 250 mg look on a gram scale
0.250 g
How do you weigh a liquid
Use the mass difference
How to prepare paper for gravity filtration
Flute it
What goes on filter flask for vacuum filtration
Büchner funnel and adapter
What is the purpose of vacuum filtration
To remove liquid mixture from final product/ solid
Where to dispose of organic solvents
organic liquid waste
Where to dispose of aqueous solvents go
aqueous liquid waste
where does paper go
contaminated paper wsate
where does glass go
yellow broken glass bin
where do tlc plates go
TLC waste bin
where do solids and boiling stones go
solid waste bin
where does clean acetone rinse go
acetone recovery
where does silica go
silica waste bin
what goes on filter flask for reduced pressure evaporation
cork or Buchner funnel filter paper and adaptor
what is the purpose of reduced pressure evaporation
remove liquid from solid, remove the solvent from sample or concentrate it
miscible
describes two liquids that are soluble in each other
density of water
1 g/mL
what two solvents are denser than water
DCM and chloroform
what is the purpose of a variac
the heating mantel can not be connected directly to the outlet or else it will become too hot and will easily vaporize contents of flask,variac which runs full power put cycles on and off prevents from happening
how to adjust setup if liquid is boiling too much or bumping
lower the lab jack & mantle, and can turn down variac
purpose of stir bars
stirring and preventing bumping
reflux set up
lack jack, mantle, stir bar, variac, RBF, condenser, tubing, hose clamps
for refill which tube does water enter from
the bottom tube
recrystallization steps
- Dissolve the solid in a minimal amount of hot solvent.
- Allow the solution to cool to room temperature.
- Cool further in an ice bath.
- Filter the mixture through a Buchner funnel to collect the solid.
- Weigh the solid to get a mass of compound recovered
- Measure the melting point
two solvent recrystallization
finding two pair of miscible solvents
- Choose solvent A that is very soluble to the compound. Choose solvent B that is does not dissolve the compound at all.
- Add hot solvent A to test tube containing compound. Heat, shake, dissolve the compound.
- Add hot solvent B. Reheat
- Cool solution
- Remove solvent via Buchner funnel to obtain crystals
TLC
thin layer chromatography
how to adjust eluent system if Rf is too low ** spots too close to baseline????
increase the polarity of eluent
what stains do we use for TLC
potassium permanganate, PMA
Aqueous or organic layer on top layer for separator funnel
Density is checked, typically organic is on the top
What is sodium sulphate used as
a drying agent
Seperation methods
Reduced pressure evaporation, vacuum filtration, gravity filtration
how do impurities effect melting point
if more than 10 degree difference then the product is impure
Info from NMR spectrum to identify
number of signals, chemical shift, integration, multiplicity
NMR downfield
left, desheilded
TMS peak on NMR
0
Solvent NMR peak
7.2 ppm
Integration NMR
area under the curve, proportional to the number of protons contained under the peak
NMR coupling
double peak on one signal, when nearby protons have a magnetic field that affect effective magnetic field. Number of peaks depends on the number of protons that are nearby and unique combinations of their spins
Spin-spin splitting is another name
n + 1 rule predicts number of peaks. N is the number of neighbors. Neighbors don’t include chemically equivalent H’s)
spin coupling
elimination of spin- spin splitting by constantly irradiating one type of nuclei at its resonance frequency
coupling constant
distance between the peaks of a multiplet
diasteromers
stereoisomers that are not mirror images
stereoisomers
molecules with the same chemical formula but different spatial arrangement
enantiomers
isomers that are mirror images of each other
what does chemical shift provide
info about the structural environment surrounding the protons producing the signal
NMR symmetry
a symmetrical compound will have one signal for multiple protons not on the same carbon
spin decoupling occurs
in the proton NMR of alcohols, amines, and carboxylic acids, resulting in the OH and NH protons appearing as broad singlets
vicinal
substituents attached to adjacent carbons
long range
attached to non adjacent carbons
Diels-Alder reaction
a [4+2] cycloaddition reaction, 2 pi bonds broken, 2 sigma bonds formed, concerted
dienophile
an alkene that reacts with a diene in a a diets-alder reaction
diene
two double bonds
dials alder mechanism
draw reaction scheme
what is in the waterless condenser
ethylene glycol
purpose of methanol in lab 3
extract crystals
green chemistry
uses materials and processes that are intended to prevent or reduce pollution at its source
lab 3
green chemistry and diets alder cycloaddition
lab 4
dreidel crafts acylation
dreidel crafts acylation mechanism
draw mechanism
friedel crafts alkylation mechanism
for CH3Cl and 1 degree RCl, the Lewis acid-base complex itself serves as the electrophile for electrophilic aromatic substitution
* with 2 and 3 degree RCl, the Lewis acid-base complex reacts further to give a 2 or 3 degree carbocation, which serves as the electrophile; carbocation formation occurs only with 2 and 3 degree alkyl chlorides because they afford more stable carbocations
friedel crafts acylation reagents
acyl chloride and AlCl3
FeCl3 vs AlCl3
AlCl3 is difficult to store and more hygroscopic than FeCl3
drawback of alkylation
further alkylation can occur, alkyl groups can rearrange into more stable carbo cations
limiting agent in lab 4, acylation
4 methods benzoyl chloride
anisole
draw image
purpose of gas trap in lab 4
to catch Hal gas
purpose of water in lab 4
quenching
purpose of ethyl acetate in lab 4
solvent
lab 5
Grignard reation
Grignard reagent
an alkyl magnesium halide that is used to make carbon-carbon bonds
Lab 5 purpose of THF
reaction solvent
Issue with Grignard reagents
they decompose in protic solvents, alcohols, and amines to form alkanes
Solvents that Grignard reagents won’t react with
diethyl ether or THF
THF
draw image
Grignard reaction mechanism
draw mechanism
organometallic compounds
compounds that contain carbon- metal bonds
wurtz coupling
coupling of two alkyl or cycloalkyl halides, produces dimers
lab 5 limiting reagent
benzophenone
side reactions of Grignard reaction
reactions with aldehydes
reactions with acyl chlorides and esters
reactions with ketones and carbon dioxide
reactions with alkyl bromide (wurtz coupling)
Grignard reactions with aldehydes
form secondary alcohols
Grignard reactions with acyl chlorides and esters
form corresponding alcohol
Grignard reactions with ketone and carbon dioxide
form tertiary alcohols and carboxylic acids
volume calculation
weight/ density
molarity
the number of moles of solute per litre of solution
% yield calculation
actual yield theoretical yield x 100
% recovery calculation
amount recovered/ initial amount x 100
% purity calculation
amount of pure/ amount of crude x 100
lab 6
borohydride reduction
reduction
gain of electrons, removal of O or addition of H
reduction of carboxylic acids
primary alcohols
reduction of aldehydes
primary alcohols
reduction of esters
primary alcohols
reduction of amides
primary amines
reduction of ketones
secondary alcohols
reducing agents
LiAlH4 NaBH4
What can LiAlH4 reduce
aldehydes, ketones, esters, carboxylic acids
what can NaBH4 reduce
aldehydes and ketones
reduction mechanism
draw mechanism
lab 6 limiting reagent
vanillin alcohol
limiting reagent
the reactant use up first in a reaction
NaOH purpose lab 6
solvent
why is NaOH a solvent for reductions
reducing agents are unstable in acids
Lab 6 HCl purpose
quenching
borohydride reduction mechanism
draw mechanism
lab 7
esterfication
esterfication
the reaction of an alcohol with a carboxylic acid to produce an ester and water
esterification mechanism
draw mechanism
TMEDA
N,N,N,N tetramethylethylene diamine (draw)
aldehyde
draw
lab 7 product polarity
product is less polar (higher up on TLC plate)
lab 8
aldol condensation
aldol
contains both aldehyde and alcohol functional groups
aldol condensation
A reaction in which an aldehyde or ketone acts as both the electrophile and nucleophile, resulting in the formation of a carbon-carbon bond in a new molecule called an aldol.
lab 8 aldol condensation catalyst
acid or base
aldol condensation mechanism
draw mechanism
