Orgo Lab Exam 2

What is the importance of working in a chemical fume hood

Protect ourselves from the noxious fumes of the chemicals

Why do we need to clamp glassware?

To prevent the glassware from tipping over

What are some everyday uses of salicylic acid

• Acne creams (Facial wash, CereVe and Cetaphil)

• Antibacterial agent

• Anti-dandruff agent

• Precursor to aspirin and Bengay relief cream

Methyl salicylate and salicylic acid are ________ products, meaning they can be found in nature

natural

What is the appearance of methyl salicylate

liquid with minty smell

How is salicylic acid synthesized

Methyl salicylate (l) reaction with NaOH and HCl to replace the ester group on methyl salicylate with a carboxylic acid group to form salicylic acid (s)

Synthesis reaction of salicylic acid

The reaction to form salicylic acid is a __________-promoted reaction

Base promoted

The based (OH-) is a nucleophile that adds to the ester and forms part of the product.

Why is the synthesis of salicylic acid base-promoted and not base-catalyzed?

the base (OH–) is the nucleophile that adds to the ester and forms part of the product. It participates in the reaction and is not regenerated later

Hydrolysis of Triacylglycerols

The three ester groups are cleaved to form glycerol and three long-chain fatty acids

Lipase-catalyzed reaction

Hydrolysis of Triacylglycerols Reaction

What is Saponification

conversion of ester functional group into carboxylic acid with a base

Experimental details: What glassware and equipment are used in the salicylic acid synthesis lab?

Erlenmeyer flask (Reaction flask)

Ring stand with clamp

Magnetic stir bar

Graduated cylinders

Hot/Stir plate (Heat and stirring will be used)

Pasteur pipettes

What reagents are used in the synthesis of salicylic acid?

methyl salicylate (l), sodium hydroxide/NaOH (l) and Hydrochloric acid/HCl (l)

How do you calculate theoretical yield?

moles of limiting reagent x mol ratio x MW of product = g of product

How do you calculate the theoretical yield of salicylic acid?

mol of methyl salicylate x mol ratio (SA/Methyl salicylate) x MW SA (g/mol) = X g of salicylic acid

What is the limiting reagent in salicylic acid synthesis?

methyl salicylate

How do you calculate precent yield

% Yield = Actual Yield / Theoretical Yield x 100

How to calculate percent yield in mulitstep synthesis

the overall percent yield is determined by multiplying the yield of each step expressed as a decimal then multiply by 100

(% yield 1 x % yield 2 x % yield 3) × 100

What is recrystallization?

Convenient way to purify a solid organic compound by using a suitable solvent.

What is the rule for selecting a good solvent for recrystallization?

The solid you are trying to purify should be soluble in the hot solvent and insoluble in a cold or room temperature solvent.

Vacuuum Filtration Schematic

In drawing of schematic include:

Buchner funnel

Adapter

Clamp on neck of vacuum flask

Ring stand

Rubber tubing

Vacuum filtration: why do we use a rubber adapter?

To ensure a tight seal between Buchner funnel and vacuum flask

Vacuum filtration: why do we use heavy-walled rubber tubing?

to prevent the tubing from collapsing from atmospheric pressure on the outside when the vacuum is applied

What is melting point range?

The temperature range with a compound changes from solid to liquid phase and loses order of crystalline lattice

Presence of impurities (purple above) will ________the observed MP range of a compound

Decrease

They disrupt the crystalline lattice of the product (salicylic acid/aspirin)

Digital MeltTemp: How to read melting point range

First reading of the range: temperature at which the solid block first begins to liquefy

Second reading of the range: temperature at which the solid is completely melted

Digital MeltTemp: Why does the sample have to be heated slowly?

Thermometer Lag – occurs when the sample melts before the thermometer has a chance to reach that temperature – leading to a depressed MP range

Broad range – is observed when melting too quickly.

Digital MeltTemp: Sample for testing MPR are placed in a _________ tube

capillary

Synthesis of Salicylic Acid: Waste Disposal Procedure

1. Collect filtrate in a 250 ml Beaker labelled “waste acidic filtrate” and neutralize it at the Neutralizing hood with NaHO3

2. Stir beaker and check pH

3. When pH is neutral (green) dispose of the neutralized solution in the sink with lots of water

Methyl salicylate is treated with ______ ______ in water to convert the methyl ester group to carboxylic acid

sodium hydroxide

Why is an Erlenmeyer flask used in the synthesis of salicylic acid lab

The sloping sides help reduce the amount of solvent the evaporates and splashing

Hazard: Sodium hydroxide and hydrochloric acid are _________

corrosive

In recrystallization, why does the solution need to cool slowly?

So the impurities will remain in the filtrate

What is another name for the filtrate or bulk solution of a reaction

mother liquor

At what approximate temperature will the reaction mixture containing methyl salicylate and 30 mL of an aqueous solution of 4M sodium hydroxide boil?

100 ºC (BP of water)

Why is it important to clamp your vacuum filter flask, even though it has a flat bottom?

Salicylic acid has some solubility in water. What would happen if you washed your crystals with too much water, during vacuum filtration?

The product salicylic acid crystals will be lost

What happens with HCl is added to solution of methyl salicylate and NaOH?

A white precipitate (salicylic acid) will form

Methyl salicylate Structure

Salicylic Acid structure

How to find mass solution using density and volume

Density x volume= mass

Why is it necessary to empty out the the filtrate from the vacuum filter flask, before pulling air over the crystals being dried inside the Buchner funnel?

The filtrate must be emptied from the flash so it does not decrease the pressure in the vacuum system when the salicylic crystals are drying

Are large crystals more likely to form when solutions are cooled quickly or slowly? and Why?

Large crystals are more likely to form when the solution is cooled slowly because all the impurities will have enough time to return to the solution

How is aspirin synthesized from salicylic acid?

the phenol group of salicylic acid is transformed into a ester group

Appearance of salicylic acid

White needle-like crystals

What are the medicinal effects of aspirin

analgesic (pain reliever)

Antipyretic (fever reducer)

Anti-inflammatory

What is the chemical name of aspirin

Acetylsalicylic acid

The synthesis of aspirin from salicylic acid is a __________ reaction

esterfication

Synthesis reaction of aspirin

Structure of Aspirin

The Synthesis of Aspirin, why is acetic anhydride in excess?

it is required to drive the reaction towards completion

In the synthesis of aspirin, acetic anhydride serves as the _________

solvent

Structure of acetic anhydride

The synthesis of aspirin is a _____-step reaction

2

What acid catalyst is required in the synthesis of aspirin?

Phosphoric acid (H3PO4)

To favor the formation of aspirin, _____ equivalents of acetic anhydride are used to every 1 equivalent of salicylic acid

3

What is the limiting reagent in the synthesis of aspirin?

salicylic acid

What is an equivalent?

The experimental mol ratio of the limiting reactant to another reactant

How do you calculate the theoretical yield of aspirin?

X g SA x 1 mol Aspirin/1 mol SA x MW Aspirin = X g Aspirin

How do you calculate the overall yield of aspirin synthesis (Lab A and B)

[(% yield from Lab A) x (% yield from Lab B) x 100

Which solvent is best for the recrystallization of aspirin? Water or ethanol?

Water because aspirin does not dissolve in water at room temperature/ cold

Aspirin purity check with Iron chloride (FeCl3): What function group reacts with FeCl3

Phenols react with FeCl3 to produce a deep purple solution, meaning there are traces of salicylic acid in aspirin product

Phosphoric acid is a _________ chemical

corrosive

Acetic anhydride is a _________ chemical and nasal ____________

corrosive and irritant

What is halogenated waste?

Chemical waste containing halogens (Cl, F, I, Br)

Aspirin synthesis: ethanol should be disposed of in _________

the non-halogenated waste container

Aspirin synthesis: solution from aqueous FeCl3 should be disposed of in _________

The FeCl3 waste container

What are the six classification of chemical hazards?

1) Flammable- Easily ignitable material with low flash point temp

2) Corrosive- Attack and destroy exposed body tissues (chemical burns)

3) Lachrymator- Causes watering in eyes

4) Carcinogen- Causes cancer

5) Teratogen- interfere with fetal development

6) Reactive- Explode (BOOM)

What are some examples of flammable chemicals?

Diethyl ether, acetone and tert-butyl methyl ether

What are some examples of corrosive chemicals?

Most are strong oxidizers, strong bases and acids

Ex: H2SO4, NaOH, HNO3, Ca(OH)2, Br2

What are some examples of lachrymator chemicals?

Thionyl chloride, Acrolein, Methacryloyl chloride

What are some examples of teratogenic chemicals?

Phenol, Benzene, Dinitrotoluene, Dioxane

What are some examples of reactive chemicals?

Na metal, sodium hydride, calcium carbide

What are some examples of carcinogenic chemicals?

Benzene, Arsenic, Methylene chloride (or Dichloromethane/DCM)

National Fire Protection Association (NFPA) Ratings

Blue: Health Hazard

Red: Fire Hazard

White: Specific Hazard

Yellow: Reactivity Hazard

Merck Index: Where can you find the density of a compound?

In the properties labeled as d25, d20 or D15

Merck Index: What does nD stand for?

The refractive index (NOT density)

What is the melting point range of salicylic acid?

158-160 C

What is the melting point range of aspirin?

134-136 C

What is the boiling point range of acetic anhydride?

138-140 C

What is miscibility?

The forming a homogenous mix between tow chemicals

Why are miscible liquids not suitable for extraction?

Two liquids are in a homogenous mixture so they cannot be separation

You must have two (miscible or immiscible) liquids for liquid-liquid extraction

immiscible

What is the physical appearance of aspirin?

White shiny crystals

Schematic for liquid extraction

Include: Ring stand, stopcock, Erlenmeyer flask, stem, sep funnel and glass stopper and short/long stem funnel

In a separatory funnel, the layers settle based on……

densities and miscibility

Structure of benzoic acid

Structure of 2-naphthol

Structure of 1,4-dimethoxy benzene

In the separatory funnel, the more dense layer is the ______ layer

bottom

Flow chart of ternary mix by extraction

Flow chart of ternary mix by extraction part 2

What are the forces that control Solubility?

Van der Waals forces

Dipole-Dipole Forces

Hydrogen Bonding

Theory of Extraction

It is always better to several smaller extraction than one big extraction because it increases the theoretical recovery of the product

How to calculate the partition or distribution coefficient K

Aqueous solution are immiscible with __________ solvents such as ether, hexane and methylene chloride

organic

What are drying agents?

Anhydrous salts that will bond with water mixed in product and retains it as a water of crystallization

Removed from product using gravity filtration

When a drying agent is added, first it clumps together, it becomes _________ when enough is added

free floating

Gravity filtration vs Vacuum filtration

Gravity filtration is used when a solute is mixed with a low-boiling solvent whereas vacuum filtration is used when it is mixed with a high-boiling organic

Gravity filtration to remove from product