orgo lab final
Partitioning
The distribution of a substance or ions between two immiscible liquids.
What is the purpose of Na2CO3?
This is a base which deprotonates the phenolic OH of tannins, rendering these compounds anionic and hence highly soluble in water but with a low solubility in the methylene chloride.vi If Na2CO3 was not present the isolated caffeine would also contain extracted tannins.
What is a MSDS and why is it important?
a detailed informational document prepared by the manufacturer or importer of a hazardous chemical. It describes the physical and chemical properties of the product
mobile phase
a medium used in chromatography which moves through the stationary phase -organic liquid =heptane(TLC) -gas=nitrogen (GC)
refractive index
a method that indirectly measures the change in the velocity of light as it passes through different material to determine the identity of an unknown substance or determine the composition of material
What is an emulsion?
a suspension of one liquid as droplets in another (the two liquids must be insoluble in one another
Chromatography
a technique in which compounds in a mixture are physically separated by partitioning between a mobile phase and a stationary phase.
flammable
able to catch fire easily
What type of extraction is used in this experiment?
acid-base
Teratogens
cause birth defects
Lachrymator
causes eyes to produce tears
What properties dictate the relative retention time of a series of chemicals?
changing column temperature, flow rate, sample size, column length
What would cause a higher % recovery for 2-Naphthol?
if the residual benzoic acid will remain in the MTBE and further react with the second base, sodium hydroxide
We use dichloromethane in this experiment, where should the excess waste be placed?
in the liquid halogenated waste container in the hood
Some black aqueous was removed with the clear CH2Cl2 layer
increase
Some water condensed on watch glass when drying
increases
too little NAHCO3
increases
What is sodium sulfate and what role does it perform?
is a dehydrating (drying) agent. It absorbs water from materials with which it comes in contact.
stationary phase
is a material used in chromatography which does not move. The mobile phase passes through the stationary phase. The stationary phase is either a pure solid powder such as alumina or silica or a thin coating of liquid on a solid support or a gel. -wax
Know safety about using concentracted NaOH
is corrosive even though it is not very concentrated. Avoid contact with skin, eyes, and clothing. Clean up all spills immediately. If accidental contact is made, wash with copious amounts of water.
What is reflux and why is it performed?
liquids boil in the lower part of an apparatus, condense in the upper part, and drip down to the lower portions again -to heat a solution in a controlled manner at a constant temperature
slower rates & lower temps=
longer Rt & better resolution
What is a LD50?
median lethal dose
What is a theoretical plate and why is it important?
one cycle of evaporation and condensation in a distillation. The more theoretical plates the better the separation
What are PPE?
personal protective equipment -googles -lab coat -gloves, etc,
Is melting point a physical or chemical property and why?
physical property b/c it used to help identify a material
Be able to calculate a corrected RI value if given a RI for water and the compound.
positive offset= subtract from RI value negative offset= add to RI value
column chromatography
rarely used as an analytical technique, as is TLC. Column chromatography is primary used to separate relative large samples into pure components. Column chromatography is a preparative technique
low bp= affect on Rt
shorter Rt
faster flow & higher temp= affect on retention time?
shorter Rt but peaks won't seperate
Why is placement of thermometer important?
so you will be able to obtain the correct temp as it is vapor before it condenses
What product forms once NaOH has been added?
sodium 2-Naphthoxide
What product forms once NaHCO3 has been added?
sodium benzoate
what do you use to remove water from dichloromethane?
sodium sulfate
What effects if any does soluble impurities have on melt point / range? Insoluble impurities?
soluble- low & broad impurity insoluble- no effect
3300
sp C-H
3000-3100
sp2 C-H
2800-3000
sp3 C-H
percent composition
the area of that peak, divided by the sum of all of the areas times 100%.
What is wavelength?
the distance from any point on a wave to an identical point on the next wave
electromagnetic spectrum
the range of wavelengths or frequencies over which electromagnetic radiation extends.
What is a flash point and what is it used for?
the temperature at which a particular organic compound gives off sufficient vapor to ignite in air. -distinguish between flammable fuels
How does the following factors influence melting point? Molecular weight, polarity,hydrogen bonding, branching
they all increase the melting point
Why was a copper mesh used?
to increase the surface area for condensation and increase the number of theoretical plates
What is the purpose of recrystallization?
to purify solid organic materials
What is the purpose of the HCl?
to treat the ion to form a neutral organic material
2100-2300
triple bonds C-N C-C
what would you have done to make spots move faster from the baseline? (TLC plate)
use a different solvent system -make it more polar
TLC
used primarily as an analytical technique. It can be used to identify components of a mixture (by comparing Rf values), monitor the progress of a reaction and check the purity of a sample (more than one spot indicates an impure sample). Rarely is TLC used to isolate and purify compounds into discrete samples.
How is wavelength calculated?
wave velocity/frequency. -λ = v/f.
retention time
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑜 𝐴 (𝑐𝑚)𝑥 (𝑚𝑖𝑛/ 𝑐m)
percentage of caffeine
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑐𝑎𝑓𝑓𝑒𝑖𝑛𝑒 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑 (𝑔) /𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑡𝑎𝑟𝑡𝑖𝑛𝑔 𝑡𝑒𝑎 (𝑔) 𝑥 100%
How is the purity of a reaction mixture determined using TLC?
# of spots -1 spot= pure ->1 spot=impure
corrosive
(adj.) eating away gradually, acidlike; bitterly sarcastic
What are the frequency ranges and groups are represented in each region?
-3200-3600 -2800-3100, 3300 -2100-2300 -1600-1800 -1000-1300
each line is one interval
B
1000-1300
C-O
1600-1680
C=C
1650-1800
C=O
2500-3600 (very broad)
COOH
Review solubility of caffeine in water and CH2Cl2.
Caffeine has a much higher solubility in hot water than room temperature (25°C) water. Therefore the caffeine is extracted from the solid tea leaves into boiling water. Then the extract is allowed to cool. Caffeine is almost four times more soluble at room temperature in methylene chloride as it is in water
Know safety about using concentracted HCl.
HCl- It is corrosive and will cause visible destruction of tissue and other materials upon contact. Avoid contact with skin, eyes, and clothing. Clean up all spills immediately. If accidental contact is made, immediately wash with copious amounts of water. Handle HCl in the fume hoods.
What are the properties of a good recrystallization solvent?
-Have a low solubility of the compound to be purified when the solvent is cold -Have a high solubility of the compound to be purified when the solvent is hot -Have a relatively low boiling point for easy evaporation from the purified compound -Does not react with the compound being purified
3200-3600 (single, pointed)
-NH
3200-3600 (broad)
-OH
What is a major safety concern when refluxing? (Hint: formation of peroxide )
-allowing too much substance to evaporate and cause peroxide to form and explode
What are some of the terms used to describe the potential dangers of a chemical compound?
-flammable -inflammable -carcinogens -mutagens -teratogens -lachrymators -explosive -corrosive -toxic
When is better to perform a factional distillation over a simple distillation?
-fractional= BP less than 50 degrees Celsius -simple= more than 50 degrees Celsius
Understand the relationship between wavenumber and energy.
-inversely proportional -In other words as energy increases, frequency increases, and wavelength decreases
The first extraction of benzoic acid and 2-naphthol why do we use NaHCO3?
-it is a weak base -to react with benzoic acid & remove benzoic acid from the MTBE so there wouldn't be a low recovery of the benzoic acid
What type of extractions take place during this reaction? (Isolation of Caffeine)
-solid-liquid -liquid-liquid
which is more polar? Rf values: .20 .50 .70
.20 -it is closer to the starting line
mutagens
A chemical or physical agent that interacts with DNA and causes a mutation.
Carcinogen
A cancer-causing substance
Which of these statements describes the relationship between frequencies in the IR.
3100 cm-1 is higher energy than 1100cm-1
What is percent recovery and how is it calculated?
= 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑐𝑜𝑚𝑜𝑢𝑛𝑑 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑/ 𝑠𝑡𝑎𝑟𝑡𝑖𝑛𝑔 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝑥 100% -to determine the amount of impurities present in the starting material
Should a melting point/ range be taken fast or slow?
A very slow rate gives good data, but is not time efficient. Best way is to ramp up temperature quickly until 20-30 degrees away from the literature value, then slowing down the rate to achieve clear results.
What would cause a low % recovery for BA?
If all of the benzoic acid does not react with the weak base sodium bicarbonate
What are the various layers in column chromatography and explain their purpose?
In column chromatography a glass or plastic tube is filled with the powder stationary phase. The mobile phase moves through the stationary phase by gravity.
Sodium Bicarbonate role in SN1 rxn
It is a weak base and will neutralize any excess acid present. When sodium bicarbonate reacts with an acid, it forms carbonic acid which dissociates into water and carbon dioxide which is a gas.
how to choose a solvent
Kb=solubility in organic solvent/ solubility in water
3200-3600 (double pointed)
NH2
What would be the end result of recrystallization in which NOT ENOUGH recrystallization solvent was used?
The obtained product would have high levels of impurities
What properties should and ideal melt point/range contain?
The range starts at the temperature the first bit of liquid is observed. The range ends at the temperature that the entire solid has disappeared
What is sodium chloride called in this reaction (not salt)?
brine
How is the identity of a product in a reaction mixture determined using TLC?
by comparing the Rf value of the sample material to the pure material
Gas Chromatography (GC)
chromatographic procedure in which a mixture of gases or highly volatile liquids is separated using a carrier gas passing through a solid, or viscous liquid on a solid support, packed in a column
Some tea spilled on while transferring to centrifuge tube.
decrease
The bag and string were weighed along with the tea
decrease
too much NAHCO3
decreases
What is the sodium chloride used for in this reaction?
decreases the formation of emulsions and promotes the separation of organic material from the water layer
Rf
distance moved by substance/distance moved by solvent -3 decimal places
combustible
easily burned
inflammable
easily set on fire; easily angered or aroused
