Orgo Lab

A student removes a chemical sample from a reagent bottle to be used in an experiment. What should he do with any excess chemical remaining from this sample after the experiment is complete?

Check and see if anyone else can use the chemical. If not, discard in the proper waste container.

wash

addition of solvent to wash away impurities while the compound of interests stays in the original layer

stationary phase

is generally comprised of a liquid or a solid material that does not move but adsorbs the components of a mixture differently based on their polaritie

How is a chemical sample introduced into a gas chromatograph?

via syringe in an injection port

Calculate the Rf value for a spot in a TLC experiment if the solvent moved 13.7 cm and the spot moved 9.8 cm.

0.72

fractional distillation - method

1) Put your mixture in a flask & stick a fractionating column on top. Then you heat it 2) The different liquids will all have different boiling points - they'll evaporate at different temperatures 3) The liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column 4) Liquids with higher boiling points might also start to evaporate, but the column is cooler towards the top, therefore they will only get part of the way up before condensing & running back down towards the flask 5) When the first liquid has been collected, you raise the temperature until the next one reaches the top *best for liquids with similar boiling points

Simple Distillation - Method

1) The solution is heated. The part of the solution that has the lowest boiling point evaporates first 2) The vapour is then cooled, condensed & is collected 3) The rest of the solution is left behind in the flask *best for distilling liquids that have very different boiling points

calculate percent composition steps

1. calculate area under each peak 2. add areas together 3. divide the area for the percent composition you are trying to figure out by the total area and multiple by 100

Suppose you are performing an extraction procedure with a carboxylic acid, like a benzoic or toluic acid. 1. Which layer should contain the carboxylic acid in a two-layer mixture of water and an organic solvent, like diethyl ether? You then add a base to form the corresponding carboxylate. 2. Which layer should contain the carboxylate in a two-layer mixture of water and an organic solvent, like diethyl ether?

1. organic layer 2. aqueous layer

In case of accidental contact with chemicals, how long should the eyes be flushed at the eyewash station?

15 minutes

Extract aniline into the aqueous layer Extract reconstituted 3-nitroaniline out of the aqueous layer Reconstitute aniline from aqueous layer Extract benzoic acid into the aqueous layer Reconstitute benzoic acid from aqueous layer Extract reconstituted benzoic acid out of the aqueous layer

5% HCl solution dichloromethane 6 M NaOH 5% NaOH solution 6 M HCl dichloromethane

You find a separatory funnel set up in a fume hood. There are clearly two visible layers. Describe a method you could use to determine which layer is the aqueous layer.

A method you could use to determine which layer is aqueous is by adding a drop of water to the top of the separation funnel. If the top layer is aqueous then the water will join it and you will not be able to see the drop added. However, if the bottom layer is aqueous then you will be able to see the water drop through the top layer and disappear as soon as it hits the bottom layer.

What is chromatography?

A technique to separate mixtures based on the molecular properties of the involved chemicals

In a TLC experiment, how do you identify the components of an unknown mixture?

Compare the Rf values of the mixture components to the Rf values of pure known compounds.

Explain what is meant by "efficiency" with respect to a distillation. Comment on the efficiency of your fractional distillation as seen by your graph.

Efficiency, with respect to a distillation, refers to the amount of heat and time required to distill the solution, along with the accuracy of the fractionation. The efficiency of my fractional distillation, as seen by my graph, seems to be fairly good as the amount of distillate seems to be at its peak at the expected boiling points for both EtOAc and BuOAc.

What information is necessary to review in order to be considered familiar with the Safety Data Sheet (SDS) of a substance?

Handling, storage, and reactivity information Identification and description of substance Hazard warnings Personal protection and first aid recommedations

Identify the precautions to take with exits in the lab.

Locate the exits prior to the start of lab. Do not block a door with an EXIT sign.

What is the first step for response to an emergency situation?

Remain calm and quiet, gather information, and assess the situation.

Which signs are typically posted in areas of active lab work?

Safety equipment signs Personal protective equipment (PPE) sign Sign prohibiting food and drink Chemical storage signs

After performing a TLC experiment, you might place the TLC plate in a container with iodine crystals. What is the purpose of the iodine crystals?

The crystals create a gas that reacts with organic compounds to help see them on the plate.

Explicitly state which volumes are likely a mixture of the two components. What percentage of the mixture volume is likely to be EtOAc and BuOAc? Explain your reasoning.

The volumes that are likely to be a mixture of the two components are 0.4, 0.3, 0.3, and 0.2, which are between the temperatures 85-115. EtOAc is likely to be 58% of the mixture volume and BuOAc is likely to be 42% of the mixture volume.

What is the purpose of a drying agent in the work up of an organic reaction?

To absorb small amounts of water in an organic solution

What is the main precaution to take if a Gas Cylinder sign is present in the lab?

Visually check that the gas cylinder is restrained but keep a safe distance from it

Immiscible solution

a solution of two mutually insoluble liquids (water and oil)

The TLC plate remains in the chamber even after the solvent has reached the top of the plate.

accurate Rf value cannot be determined

The solvent line is not marked after the TLC plate is removed from the chamber.

accurate Rf value cannot be determined

The first signal viewed on a gas chromatograph is the ______ peak

air

How can you quantify the relative amount of one component in a two-component mixture based on the signals on a chromatograph?

area A/(Area A + Area B) x 100

preferential solubility

at equilibrium different components are going to have a preference for different solvent

Aniline involves an amine, which is a _________ functional group. When an aqueous acid solution is added to an organic solution including aniline, the aniline appears in the ________ in its ______ form. Then, a base is added to _______ the aniline.

basic aqueous protonated reconstituted

mobile phase

carries the sample compounds along the stationary phase and can be a variety of liquid or gas solvents

Raoult's Law

chemical law that states that the vapor pressure of a solution is dependent on the mole fraction of a solute added to a solution P(solution)=X(mole fraction of solvent)*P(vapor pressure of pure solvent)

After each chemical component reaches the end of the column in a gas chromatography experiment, it hits the

detector

In order for a substance to be an effective mobile phase in a chromatography experiment, it must be able to move

different components of a mixture at different rates

Safety Data Sheet recommended personal protective equipment (PPE)= chemical name and formula= possible dangers and health effects= incompatibility or reactivity with other chemicals= recommendations in case of accidental contact with the chemical=

exposure control/personal protection Identification Hazard identification handling and storing first aid measures

Moves desired compound from one layer to another Leaves desired compound in its starting layer Often involves a reaction in one of the layers Moves impurities from one layer to another Leaves impurities in their starting layer

extraction wash extraction wash extraction

NFPA Diamond red= yellow= white= blue=

flammability reactivity special hazards health

What hazards are associated with naphthalene?

flammable toxic produces nauseating vapors

chromatography

general term for a separation strategy of a mixture based on the properties of the components

In a gas-liquid chromatography experiment, the stationary phase is a ________is the mobile phase is a _______. The mechanism of separation is ________

liquid gas partitioning

Suppose a polar solvent is required for separation of a mixture in a chromatography experiment. Which solvent would be the best choice?

methanol, CH3OH

To run a thin layer chromatography experiment with a chemical substance, begin by marking a horizontal line near the bottom of a TLC plate with _________. Place a _______ spot of the substance onto the line. For the mobile phase, add a small amount of ________ at the bottom of a TLC chamber. Place the plate in, then __________the chamber. Once the mobile phase approaches the top of the plate, remove the plate and mark the _________ line. Note the position of the spots and calculate Rf values if needed.

pencil small solvent cover solvent

Identify the mechanism of separation via gas chromatography.

phase distribution

adhesion

property of different molecules to cling to each other. Generally, gases have weak cohesion

cohesion

property of molecules of the same substance to stick to each other due to mutual attraction

distillation

purification and separation technique for liquid mixtures that uses selective boiling and condensing

Identify the types of information that can be obtained from a gas chromatography experiment.

quantitative qualitative preparative

The order of peaks in the spectrum= The area under a peak in the spectrum= The width of a peak in the spectrum=

relative boiling points of substances amount of substances present adsorption of the substance by the column

Caution must be taken when injecting a sample into the injection port, mainly due to the facts that the syringe is ______ and the injection port is _______

sharp hot

Pen rather than pencil is used to draw the lines on the plate

smears on TLC plate

In a gas-solid chromatography experiment, the stationary phase is a _______ is the mobile phase is a ________. The mechanism of separation is _________

solid gas adsorption

Identify the factors that affect retention time.

temperature of column length of column flow rate of gas phase polarity of liquid phase

vapor pressure

the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system.

The mobile phase used does not move any of the spots at all

there can be no separation of components

azeotrope

type of mixture that cannot be separated by distillation any further; ex. 95% ethanol and 5% water bc boiling points too close

What is the best listed approach for viewing spots that are not visible on a TLC plate?

use UV lamp

retention times (Rf values)

used to compare the distance the individual components travel to the distance the solvent (or mobile phase) moves =distance traveled by component/distance traveled by the solvent

extraction

utilizes solubility or reactivity to pull the compound of interest from one layer into the other

Suppose you are going to perform a TLC experiment, which materials will you use to prepare the TLC development chamber?

watch glass beaker filter paper