What is a Material Safety Data Sheet (MSDS) and what data does it usually contain?
Technical bulletin listing physical and chemical properties, hazards, etc of a lab reagent
Define rules about eating, drinking, and applying cosmetics in lab.
no eating, drinking, or applying cosmetics in lab.
What does bumping mean and how to avoid it?
Sudden release of vapor; use boiling chips
National Fire Protection Association's Diamond
0 (low) and 4 (high)
blue - health
red - fire
white - specific hazards
yellow - reactivity
What to do if spill on skin
immediately wash off skin with plenty of water, and let TA know.
If spill on person what do you do?
Use sink or safety shower as necessary. Remove clothing (all). Do not remove safety goggles b/f washing reagent from face (this will lessen the likelihood of getting reagent in eyes).
Define the term: melting point
Temperature at which solid compound is in equilibrium with its liquid
Define the term: melting point range
Temperature range between start of liquid formation till all the solid becomes liquid
Define the term: impurity
Any admixture in the compound of interest
Define: eutectic composition
when both solids are in equilibrium with the liquid
Define: eutectic temperature
the lowest possible melting point for a mixture of X and Y
Describe the purpose and technique of taking mixture m.p.
To proof identity of unknown compound: mix known and unknown compounds. If mixture mp is the same as mp of known compound, unknown and known compound are the same
Explain the phenomena (name the process): compound to melt is darkening when heating and release gas when melting
Decomposition
Explain the phenomena (name the process): compound disappears from capillary when attempting to measure its m.p.
Sublimation
Define: orientation mp
if mp is unknown then first measure the approximate melting point of the compound. Then you let appratus cool to 15 degrees below the orientation mp; new sample is heated increasing the temp at 1-2 degrees Celsius per minute to get the accurate mp.
Errors in observed mp
1) placement of too much sample into the capillary tube (poor heat transfer) - should be 2-3 mg
2) not grinding particles (poor heat transfer)
define: sweating
droplets on outside surface of sample, due to insufficient drying
define: decompose
darkening in the color of the compound as it melts
define: sublimation
passes directly from solid to vapor, the compound disappears - sample vaporizes and recrystallizes higher up in capillary tube
In distillation Term volatile is related to a chemical having (true or false):
1) Low pressure at high temperature
2) High pressure at high temperature
3) High pressure at low temperature
1) F
2) F
3) T
Define: distillation
technique used for separating compounds based on differences in their bp
Distillation was made using 15 mL of each cyclohexane and toluene. With what scale:
Macro
define: pot
where volatile compounds are heated to boiling in one container
define: condenser (explain how used)
where the vapors that are produced are then cooled and re-liquefied by passing them through a water cooled condenser
define: receiver
where the re-liquified cooled produces are collected
define: evaporation
transition from liquid to vapor on only those molecules at the liquid surface (happens at temp below the bp of compound)
define equilibrium vapor pressure:
pressure exerted by these gaseous molecules on the walls of the container
Define: boiling point
Temperature, at which vapor pressure of liquid equals external pressure
define: miscible
liquids mix
Distillation of miscible liquids best described using:
Rault's Law
Write the equation for Rault's law and define the terms
PT = P1X1 + P2X2
PT - total pressure
P1,2 - partial pressure
X1,2 - molar fraction of component
Define: distillate
when the vapors condense into a liquid, and have the same composition as the vapors formed
Define: simple distillation
if one compound is much more volatile than the other
What makes fractional distillation different from simple distillation?
it has a fractionating column between the pot and distilling head
True or False: Vapors over the mixture of cyclohexane and toluene contain the higher percentage of cyclohexane than that in mixture
True
B.p. of mixture of 2 liquids is always (T or F)
1) Lower than b.p. of both components
2) Higher than b.p. of both components
3) In between the b.ps. of both components
1) false
2) false
3) true
True or False: Fractional distillation is preferable if difference in b.p. of mixture components is lower than 40 degrees C
True
State two rules not to break when performing distillation
Do not distil to dryness
Do not heat closed system
Define: recrystallization
purification process used to remove impurities from organic compounds that are solid at room temp
Define: oiling out
when a compound is insoluble in a solution at a temp above the compound's mp. As a result the compound is deposited as an oil, and not crystals
How to choose a good solvent
room temp: insoluble
bp: soluble
ice: insoulble
Define: solvent pair
two solvents are used to dissolve compound
define: filter flask
flask with a sidearm
equation for percent recovery
(mass of recrystallized compound in g /
mass of crude compound in g) (100%)
How to tell is compound is pure
it melts at a range of 1-3 degrees Celsius near its reported melting point
If crystals don't form what can you do?
1) scratch glass to give crystals sites to form
2) put seed crystal of pure compound into the soln
If solution has colored impurities
add activated carbon
How to avoid premature crystallization in the funnel stem
heat funnel, filter paper, and collection flask
Define: eluent
a solvent used as a mobile phase
TLC
thin layer chromatography
Equation for Rf
distance traveled by comp, mm /
distance traveled by solvent, mm
define: eluent front
the point that the eluent has reached
the more polar the eluent
the greater its eluting power, ability to move compounds over the absorbent surface
Name 3 main parts of Gas Chromatograph
Injector, column, detector
Chromatogram after analysis of some mixture shows several peaks. Ratio of components in the mixture is proportional to:
Area peaks
What solvent was suitable for separation of 2 polar compounds using silica gel:
toluene or ethyl ether
State 2 methods of visualizing TLC plates
Under UV-light or in iodine chamber
Write the equation for the % recovery in column chromatography
(mass of recovered compound /
mass of compound in original mixture) (100%)
Calculate the mass of components in 170 mg of 1:1:3 mixture (by mass) of ferrocene, acetylferrocene and alumina
1+1+3 = 5 parts total;
170mg/5parts = 34mg [1 part] of each ferrocene and acetylferrocene; 34x3[parts]=102mg of alumina
Describe the consequences of column dry-out during a separation
Air bubbles will form in sorbent bed. Those bubbles may prevent solvent from moving through bed, and mixture to separate
Define: Extraction
process that selectively dissolves one or more of the mixture compounds into an appropriate solvent
define: washing
reverse process of extraction, in which the impurities are removed to the second solvent, leaving the desired compound in the original solvent
define: emulsion
suspension of small droplets of one liquid into another liquid
Codistillation (including steam distillation) is possible if components of mixture are:
Immiscible
State why Steam distillation is preferable for compound that boils at high temperature (>250 C at 1atm)
Distillation of compound at lower temperature lower risk of thermal decomposition
Clove oil components are:
eugenol
eugenole acetate
Will eugenol or eugenol acetate react with sodium hydroxide? What functional group will the reaction occur at?
eugenol
on the -OH group
When two liquids are immiscible the equation used is?
Dalton's Law
Match the compounds and reagents used to separate mixture by extraction:
acetanilide NaOH
t-butylphenol none
p-Toluic acid NaHCO3
acetanilide - none
t-butylphenol - NaOH
p-Toluic acid - NaHCO3
Describe how properly release pressure buildup in separatory flask during the extraction
Turn separatory funnel upside down and carefully open stopcock
Calculate % recovery of each component if 1.0 g each acetanilide, t-butylphenol and p-toluic acid isolated from 4.3 g of 1:1:1 mixture (molar ratio)
acetanilide MW = 135 g/mol
t-butylphenol MW = 150 g/mol
p-toluic acid MW = 136 g/mol
If 1 mole of each component, mass of mixture will be 135+150+136=421g
4.3g of mixture will correspond to 4.3/421=0.0102mole of each component
Starting amounts:
Acetanilide, g = 0.0102mole x 135g/mole = 1.37g;
t-Butylphenol, g = 0.0102mole x 150g/mole = 1.
Sterochemistry
right is R
Left is S
Assuming solvolysis of 2-chloro-2-methylpropane proceeds as SN1 reaction, does rate of reaction depends on NaOH concentration?
No