CHEM 0330 - Labs

Why do you need to support a vacuum filtration apparatus with a clamp?

- The filter funnel makes the apparatus top-heavy. - The thick-walled vacuum tubing makes the flask tippy.

Identify characteristics that describe a Grignard reagent.

- nucleophile - basic

LAB 3::::: In general, when hydrocarbons like oil are added to water, the two liquids _____1_____ because hydrocarbons are _____2_____ and water is _____3_____.

1. do not mix 2. non-polar 3. polar

LAB 8::::: Consider the charge distribution of a Grignard reagent. There is a partial _____1_____ charge on Mg−X, where X is a halogen, and a partial _____2_____ charge on the adjacent carbon.

1. positive 2. negative

Appropriate personal protective equipment (PPE) is essential in the organic laboratory. Recommended items include _____1_____ to protect the body, _____2_____ as eye protection, and _____3_____ to cover the hands.

1. a lab coat 2. goggles 3. gloves

Once the vacuum filtration set-up is complete, start by _____1_____ in the filter funnel. Then, _____2_____ the mixture _____3_____.

1. adding a small amount of water 2. slowly decant 3. into the middle of the filter paper

How many sections are in an SDS?

16

When using a separatory funnel, you should vent the funnel. What does the term venting mean?

Opening the stopcock to relieve pressure build-up within the funnel while inverted

What is the purpose of crushing the Excedrin tablet?

To make it easier for the Excedrin components to dissolve in solution

What is the purpose of preparing three different TLC chambers?

To test three different solvent systems for the mobile phase that gives the best separation

Determine when you should remove your goggles in the lab room.

When everyone in the room is done handling any chemicals or glassware

Why is it necessary for the recrystallization solvent to be maintained at high temperature while dissolving the crude benzoic acid?

- A hot solvent allows for increased solute solubility - A hot solvent reduces crystallization during hot gravity filtration - Having the solvent hot allows recrystallization to occur as the solution cools as long as the solution was saturated at the hot temperature.

Which statements below are true regarding a chemical mixture?

- A material made up of two or more substances in which their identities are maintained. - A chemical mixture can be homogeneous or heterogeneous.

What are the best practices while sharing a lab balance with other students?

- Appropriately clean the balance area after use. - Alert your TA or instructor about any issues with the balance.

In a steam bath used in Pitt Teaching Labs, which statements are true?

- Condensed steam drains out the bottom hose as water into a cup sink. - Steam enters through a hose in the top inlet of the steam bath from the steam line.

When using vacuum filtration to separate two solids, what techniques should you use to ensure a quantitative separation?

- Dry the solid on the filter paper after the separation. - Carefully rinse the flask into the filter funnel with a small amount of water. - Wash the solid on the filter paper with a small amount of water. - Wet the filter paper before pouring the mixture into the filter funnel.

A hot filtration needs to be performed quickly to avoid crystallization in the glassware. Identify the appropriate practices you can use to prevent unwanted crystallization.

- Flute the filter paper before heating the funnel. - Use a short-stemmed funnel in the filtration.

Which statement(s) are true when aqueous sodium hydroxide is added to the filtrate solution (that has been transferred to the separatory funnel)?

- Immiscible liquids are now present in the separatory funnel - An aqueous solution with a high pH was added to the funnel. - As the benzoate ion was formed, hydroxide ion was consumed. - Benzoic acid was converted into water-soluble benzoate ions.

What should you do every time you are setting up glassware for a vacuum filtration?

- Inspect the tubing for any holes. - Ensure that the glassware is designed for use with a vacuum. - Check that there are no cracks or defects in the glassware.

Why does the chemist transfer methanol from the 4 L bottle into the 50 mL beaker and then from the 50 mL beaker into the graduated cylinder rather than transferring methanol directly from the 4 L bottle into the graduated cylinder?

- It is safer to pour into an intermediate container that has a larger mouth so that methanol is less likely to spill when filling the 10 mL graduated cylinder. - A 50 mL beaker has a pour spout that will allow for neater transfer to the graduated cylinder.

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

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

SDS purpose

- Provide a guide for the safe use of a hazardous chemical. - Alert a chemist to the inherent hazards associated with a chemical.

If crystal growth does not start on its own after the solution in the flask returns to room temperature, identify the best ways to promote crystal growth.

- Scratch the bottom of the flask gently with a stirring rod. - Add a seed crystal.

Why does the chemist carefully trace a baseline with a pencil straight across the plate at least 1-2 cm from the bottom of the plate?

- The baseline needs to be the same distance from the bottom of the plate for all of the spots in order to calculate accurate Rf. - A pencil is used instead of a pen because a pen will result in ink streaking across the plate, making analysis of the plate difficult or impossible. - The baseline must be above the solvent level in the TLC chamber so that the baseline spots do not dissolve into the mobile phase at the bottom of the chamber.

Consider the boiling stones added to the mixture (and solvent) before heating. Which statements are true?

- The boiling stones prevent hot pockets of vapor from building up in the heated solvent, which if left unchecked, can lead to violent bumping, splashes, and boil overs. - The ether-insoluble cellulose could have served the role (prevent bumping) of the boiling stones - It is good practice to be in the habit of adding boiling stones to all liquids that are going to be heated in the laboratory.

Once the ground Excedrin tablet is dissolved in DCM, why is the solution gravity-filtered? Check all that apply.

- To remove binding reagents from the dichloromethane extract. - To remove insoluble compounds like acetaminophen from the dichloromethane extract - To isolate the solid extract, which can then be dissolved in a different solvent and analyzed as well

Before adding a sample or solvent to a separatory funnel, what should you have in place?

- a flask under the separatory funnel - a funnel in the top of the separatory funnel - a stopcock in the closed position

Identify the characteristics of a good recrystallization solvent.

- dissolves a chemical sample well at high temperatures - does NOT dissolve a chemical sample well at low temperatures

molecules that cannot be separated by an acid/base extraction

- two molecules that do NOT have significant acidic or basic characteristics - two molecules with similar acidity/basicity

In order to dissolve a chemical sample in a recrystallization solvent, add the room-temperature solvent _____1_____ in an Erlenmeyer flask on a hot plate. Turn on the heat, starting at _____2_____. Using a _____3_____, add additional solvent from a second container on the heat source. Swirl the sample flask after each addition, and try to add _____4_____ in order to dissolve the solid.

1. just until it covers the sample 2. a low setting and increasing gradually 3. pipet 4. as little solvent as possible

After a recrystallization, a pure substance will ideally appear as a network of _____1_____. If this is not the case, it may be worthwhile to reheat the flask and allow the contents to cool more _____2_____.

1. large crystals 2. slowly

LAB2::::: Proton NMR is a technique that uses _____1_____ to study the _____2_____ in a sample.

1. nuclear magnetic resonance 2. hydrogen atoms

Read each statement regarding food and beverages in the lab and determine if each is true or false. 1. Tobacco products of all kinds are prohibited in lab. 2. Beverages are allowed in lab as long as they are in containers with lids. 3. Chewing gum is okay in the lab as long as you don't blow bubbles. 4. Food items should not be brought into the lab.

1. T 2. F 3. F 4. T

A Grignard reagent is prepared when _____1_____ reacts with _____2_____ in the solvent _____3_____.

1. an organohalide 2. magnesium 3. ether

In an NMR experiment, shielding refers to the reduced impact of the _____1_____ on a nucleus due to the presence of _____2_____ around the nucleus. Shielding can be _____3_____ by the presence of more electronegative groups around the nucleus. A shielded nucleus appears further _____4_____ whereas a deshielded nucleus appears further _____5_____ in an NMR spectrum.

1. applied magnetic field 2. electrons 3. decreased 4. upfield 5. downfield

Match each lab incident to the item of PPE that will protect you from it. 1. While pulling an empty beaker off the shelf at the beginning of lab, it slips out of your hand onto the floor. 2. While checking on a stirring solution, the solution splashes up towards your face. 3. While picking up a buret, an unknown solution left by a previous solution drips onto your hand. 4. While transferring a solution from a flask to a beaker, the solution accidentally spills down the front of the lab bench.

1. closed-toe shoes 2. goggles 3. gloves 4. lab coat

When using acids and bases, note that these substances are _____1_____. Make every effort to avoid contact with _____2_____. Be sure to wipe up any spills _____3_____.

1. corrosive 2. the skin and lab surfaces 3. immediately

Changing gloves often will minimize the spread of chemicals. To properly remove gloves, first,_____1_____, and then, _____2_____. Then insert _____3_____ between the interior edge of the second glove and the skin, and remove the second glove.

1. grasp the exterior of one glove with a gloved hand 2. peel off the first glove 3. a bare finger

Hot filtration is a type of _____1_____ filtration in which the glassware is _____2_____. Hot filtration is useful to _____3_____ in processes like recrystallization, in which solubility of the desired compound is dependent on _____4_____.

1. gravity 2. used at a high temperature 3. remove solid impurities 4. temperature

Arrange the following recrystallization steps in the correct order:

1. heat methanol to a boil 2. slowly add hot methanol to crude solid until just dissolved 3. perform hot gravity filtration to remove insoluble material 4. Leave filtrate in hood to slowly cool to room temperature 5. Place cooling filtrate in an ice bath to promote recrystallization 6. Collect product by vacuum filtration and weigh pure crystals

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

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 _____1_____. Place a _____2_____ spot of the substance onto the line. For the mobile phase, add a small amount of _____3_____ at the bottom of a TLC chamber. Place the plate in, then _____4_____ the chamber. Once the mobile phase approaches the top of the plate, remove the plate and mark the _____5_____ line. Note the position of the spots and calculate Rf values if needed.

1. pencil 2. small 3. solvent 4. cover 5. solvent

When using the Tare function on a balance, start by _____1_____. Then, _____2_____ to cancel out that mass. Finally, _____3_____ and record the mass of your sample.

1. placing the glassware on the balance 2. press the Tare/Zero button 3. add your sample to the glassware

After mixing the solutions in a separatory funnel, the stopper should be _____1_____ and the liquid should be _____2_____ and the layers allowed to separate. When you get close to the interface between the layers, _____3_____ the funnel and _____4_____ until the first layer is collected. _____5_____ to collect the second layer.

1. removed 2. drained through the stopcock 3. get eye level with 4. slow the draining 5. switch to a new flask

The appearance of multiple peaks for a single nucleus due to neighboring nuclei _____1_____. The frequency at which a nucleus absorbs and resonates with a magnetic field _____2_____. The area of a signal that corresponds to the number of nuclei at that frequency _____3_____. The end of the NMR spectrum far from the reference signal _____4_____. The end of the NMR spectrum close to the reference signal _____5_____.

1. splitting 2. chemical shift 3. integration 4. downfield 5. upfield

Identify the effect of each error during a thin layer chromatography experiment. 1. Pen rather than pencil is used to draw the lines on the plate. 2. The mobile phase used does not move any of the spots at all. 3. The TLC plate remains in the chamber even after the solvent has reached the top of the plate. 4. The solvent line is not marked after the TLC plate is removed from the chamber.

1. there will be smears on the TLC plate 2. there can be no separation of components 3. accurate Rf values cannot be determined 4. accurate Rf values cannot be determined

To determine the layers in a separation of organic and aqueous solutions, you can add a small amount of _____1_____ to the top. If the top layer is aqueous, the addition will _____2_____ the top layer. If the bottom layer is aqueous, the addition will _____3_____ the top layer and _____4_____ the bottom layer.

1. water drops 2. combine with 3. travel through 4. combine with

True or False? A crystal structure with impurities will have a higher melting point range.

F

How is a flammable liquid defined and what is a flash point?

A flammable liquid is defined as a liquid having a flash point of 93 degrees C and lower. A flash point is the lowest possible temperature at which a flammable liquid can give off sufficient vapor to form an ignitable mixture with air near its surface or in a vessel; ultimately the lowest temperature at which a flammable liquid can be flammable

What is the difference between a hazard and a risk?

A hazard causes or has the potential to cause harm. A risk is the probability that a hazard will cause harm.

Briefly explain the difference between acute and chronic exposure.

Acute exposure is one exposure that occurs in a short period of time, usually to high concentrations/amounts of material. Chronic exposure is repeated exposure over a long period of time, usually to low concentration/amounts of material. Chronic is a more gradual exposure than acute.

What is the difference between an irritant and a corrosive chemical?

An irritant causes temporary inflammation or irritation while a corrosive chemical causes irreversible damage. A corrosive chemical is, in the long term, more detrimental than an irritant.

What is the best course of action if solid material remains in the flask after the heating step of a recrystallization?

Filter the hot mixture.

Which section of an SDS includes GHS pictograms and precautionary statements?

Hazard(s) Identification

Which property is the basis of the purification technique recrystallization?

solubility

The substance to which the sample is bound at the start of an experiment

stationary phase

A Grignard reagent added to a ketone will form what kind of alcohol?

tertiary

What is the purpose of the Claisen adapter in the reflux setup?

to allow for addition of reagents (via addition funnel) without removing the condenser

Why was the mixture swirled and heated upon adding the solvent?

to more fully dissolve the components of the mixture

Why is it important to use a drying tube?

to prevent destruction of the Grignard Reagent

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

use a UV lamp

What should you do every time before you leave the lab?

wash your hands, remove your gloves, remove your lab coat (if you're wearing one)

Grignard reagents are very good bases, and they can be destroyed by what?

water, ethanol, butyric acid, methanol (protic solvents)

Which is NOT a good source of information about the hazards that affect waste disposal in a chemistry lab?

your lab partner

Why should Bunsen burners not be used when heating organic materials?

Many organic materials are flammable and could cause a fire.

A value that quantifies the distance traveled by a substance relative to the distance traveled by the solvent

Rf

Your goal is to separate two solids by adding water and then filtering the mixture. What are the final steps of ending up with two separate solids? Assume only one of the solids is water soluble.

Scrape the solid off the filter paper into one container and evaporate the water from the filtrate to isolate the other solid.

Why is it a good idea to use UV light to visualize the undeveloped TLC plate before developing it in the TLC chamber?

So you can tell if your spots are too big or too small and make another TLC plate if needed

Why are steam baths considered a safer way to heat organic liquids than hot plates?

The risk of fire when working with flammable solvents is reduced.

Which key feature is formed in a Grignard reaction?

carbon-carbon bond

What type of gloves were used when handling dichloromethane (DCM)?

chemically-resistant

Calculate Rf

distance spot moved / distance solvent moved

Which section of an SDS provides information about PPE?

exposure controls/personal protection

Which section of an SDS gives advice about how to respond if a person is exposed to a chemical?

first-aid measures

Charcoal is often times added to a recrystallization solution that:

has a colored impurity

The substance that carries the components of a mixture

mobile phase

organic layer

non polar

In this lab, benzophenone is added to phenyl magnesium bromide, a Grignard reagent. The Grignard reagent in this chemistry acts as the

nucleophile

Identify the best support for a separatory funnel.

Iron ring clamped to a ring stand

Which section of an SDS provides physical property data such as melting and boiling points?

physical and chemical properties

aqueous layer

polar

LAB 1::::: NFPA diamond color meanings

blue-health red-flammability yellow-reactivity white-special hazards

From the perspective of synthetic chemists, what potential disadvantage do steam baths have compared to hot plates for heating?

Some reactions, like Grignard reactions, are water sensitive

If there is no diethyl ether in the lab, what other solvent can you use as an alternative?

THF (polar aprotic, non-reactive solvent)

Hot filtration is a technique in which the mixture is heated and all the glassware is also heated for the filtration. When should you use the technique of hot filtration?

When you are separating a slightly soluble solid from an insoluble solid

You notice that you have leftover magnesium. What do you do with it?

Your instructor will dispose of it in a specially labelled isolated waste.

LAB 4::::: What is chromatography?

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

What is a signal word?

A word on a label that alerts users about a substances hazard level, like "warning" or "danger."

Determine when to put on disposable gloves for work in the lab.

Before handling any glassware or chemicals for the experiment

Which substance would not work as a Grignard reagent? Why? A) Ethylmagnesium bromide B) Phenylmagnesium chloride C) Isopropylmagnesium chloride D) Methylcalcium bromide

D - The structure of the organic portion and the identity of the halide may vary, but the alkali earth metal must be magnesium.

What is the best reason for the glove choice used to handle DCM?

DCM more quickly breaks through nitrile and latex gloves than it breaks through chemically-resistant gloves.

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

beaker, filter paper, watch glass

What would happen if too much analgesic/analyte was spotted on a TLC plate?

The spot would streak up the plate, making it very difficult to calculate an accurate Rf.

In lab, you may need to evaluate the odor or smell of a chemical. What is the best way to smell a chemical sample?

Use your hand to gently waft the smell toward you.

Determine the safest option in the lab if you need your vision to be corrected.

Wear corrective glasses or lenses under your safety goggles for the whole experiment, but always check with your TA or Instructor for your school's policy

When should lab participants look at the Safety Data Sheet (SDS) of a substance?

before using the substance

When creating a diluted sulfuric acid solution, you should...

add acid to ice then add icy acid to water

A base extraction involves:

adding a basic aqueous solution to deprotonate acidic functional groups

An acid extraction involves:

adding an acidic aqueous solution to protonate basic functional groups