Organic Chemistry Lab Final

What does a typical diels alder reaction require

heating

Why did the diels alder reaction performed in lab not need heating

very reactive diene (cyclic) and dienophile

Why does 1,3 butadiene prefer an s-trans conformation

avoids steric repulsion between terminal methylene groups

What increases the reactivity of the dienophile

electron withdrawing groups (halogens, carbonyls, nitriles)

What is the reactive cyclic diene used in the diels alder reaction

furan

What is the reactive, electron-deficient dienophile used in the diels alder reaction

maleic anhydride

What is the “textbook” feature of diels alder that the lab appears to violate

predicts major product of diels alder is endo

What is formed 500 times faster in diels alder

endo product

Why is the exo product created in this diels alder lab

an equilibrium is established

What are the safety concerns associated with furan and tetrahydrofuran

flammable, possible carcinogen

How should furan and tetrahydrofuran be handled

closed containers when transported between fume hoods

What are the hazards associated with maleic anhydride

allergic skin reaction or breathing difficulties

What can aromatic hydrocarbons be used for

building blocks for larger campounds

For less reactive arenes, what must be used to add a halogen to the aromatic ring

lewis acid catalyst like FeX3

In the bromination experiment, the acetanilide is reactive enough towards bromine that

no catalyst required

In the bromination experiment, the acetanilide is just unreactive enough towards bromine that

you can isolate a monobrominated product

Why is liquid bromine not used in lab

fuming liquid capable of causing severe burns

Why is concentrated acetic acid not used in lab

pungent odor and causes burns

What is used instead of the dangerous liquid bromine and concentrated acetic acid mixture

sodium hypochlorite (NaClO) and sodium bromide

Why is the insitu generation of Br2 much safer than handling acidic solutions

the bromine generated is consumed immediately by the electophilic aromatic substitution reaction

What is any excess bromine remaining in the electrophilic aromatic substitution reaction reduced back to

bromide by addition of sodium thiosulface

What is sodium thosulfate used for in the bromination lab

reducing agent

What is sodium hydroxide added for in the bromination lab

decreases the solubility of the product and improves yield W

What are the safety risks associated with acetanilide

may cause allergic reaction

What are the safety risks associated with glacial acetic acid

flammable, corrosive, lachrymator (irritation to eyes and mucous membranes)

How should glacial acetic acid be safely handled

use in fume hood and transport in closed container

What are the safety risks associated with ethanol

highly flammable

What are the safety risks associated wtih sodium hypochlorite

oxidizing agent and can release toxic fumes

How should sodium hypochlorite be used safely

the fume hood

What are the safety risks associated with sodium hydroxide

caustic (severe burns), hygroscopic (readily absorbs water from air), and deliquescent (absorbs so much water from air that it will dissolve into aqueous solution)

How must sodium hydroxide be handled safely

containers closed immediately after use, spilled pellets disposed of immediately before they turn into caustic (corrodes tissue) liquid

What are the safety risks associated with sodium bromide and sodium thiosulfate

irritants

How are azo dyes formed

reacting an aromatic compound with a diazonium salt

How is the diazo functional group (N2+) formed

reacting the corresponding amine with nitrous acid (HNO2)

How is the diazo functional group formed in lab

sodium nitrate (NaNO2) and hydrochloric acid

Why do diazonium salts tend to be highly unstable

N2 is one of the best leaving groups

What is done in lab to help the stability of the N2

ice bath

What must be present because the diazo group has a positive charge

a counterion

What counterion is present in the diazo coupling portion of the lab

chloride (from HCl)

What ionic product is present in the diazo coupling lab

salt

What is the milky slurry of diazonium salt added to

coupling partner, 2-naphthol

What is the mechanism of the diazo coupling itself

electrophilic aromatic substitution

What is the electrophile in the diazo coupling reaction

terminal nitrogen of the diazonium ion

What does the hydroxyl serve as in the Orange II lab

activating ortho/para directing functional group

Why is the hydroxyl an activating ortho/para functional group

lone pairs on oxygen stabilize the cation

What are the hazards associated with sodium nitrite

oxidizing agent

What should not be done with sodium nitrite unless directed to do so

combining with organic material

What is the hazard associated with sulfanilic acid

allergic skin reaction

What is the hazard associated with sodium carbonate and hydrochloric acid

will generate carbon dioxide (with gas evolution) when combined

What is the hazard associated with 2-naphthol

toxic to aquatic life

What is the hazard associated with Orange II

skin, eye, respiratory irritation

What is done in the Orange II lab with the water-soluble product

salting out by adding NaCl

What does salting out your water soluble product do

reducing solubility of an organic compound in an aqueous solution

How does salting out your product reduce solubility

water molecules busy keeping salt ions dissolved reducing ability to keep the product’s molecules dissolved as well

Why do you wash your product with saturated salt instead of water in the Orange II lab

to minimize loss of product in the filtrate - product water soluble

What do reversible reactions of nucleophiles to carbonyl groups feature

nucleophiles that are viable leaving groups

What do irreversible nucleophile to carbonyl group reactions feature

nucleophiles that are not viable leaving groups

Why are many compounds with B-H or Al-H bonds used as reducing agents

hydrogen is more electronegative than boron or aluminum (sources of hydride)

What is more reactive, LiAlH4 or NaBH4

LiAlH4 is much more reactive and can reduce functional groups like esters and amides

What is a situation NaBH4 would be more desirable in

protic solvents - LiAlH4 would react violently

What is the hazard associated with LAH on larger scales

evolution of flammable hydrogen gas and the heat from the exothermic reaction

What are the safety hazards associated with sodium borohydride

reacts with water to release flammable hydrogen gas

How can hazards associated with sodium borohydride be managed

keep containers closed

What are hazards associated with methanol

flammable organic solvent toxic through inhalation

How should methanol be used to reduce hazards

only in fume hood, keep away from sources of ignition

What are hazards associated with hydrochloric acid

caustic (burn/corrode tissue)

What is the class of hydrocarbon natural products whose structures can be formally described as constructed from 5-carbon isoprene units

terpenes

How are terpenes different from terpenoids

contain other non-hydrocarbon functional groups

What are terpenes and terpenoids major constituents of

plant resins and oils

What is used to convert alcohols to ketones

sodium hypochlorite (oxidizing agent)

When using sodium hypochlorite (household bleach) when converting alcohols to ketones, in the presence of acid, what is presumably formed

hypochlorous acid

What can hypochlorous acid do

oxidize the alcohol

Why is household bleach not used for our oxidation reaction

can vary in concentration, diminishing over time and inhalation hazard

how will hypochlorite be generated in our oxidation lab

oxidizing chloride (frome NaCl) with Oxone

What is Oxone

triple salt containing potassium peroxymonosulfate as the active oxidizing agent

What is Oxone used to oxidize in this experiment

chloride to hypochlorite

Why is only a catalytic amount of chloride needed for the oxidation reaction

Chloride is regenerated when the alcohol reacts with hypochlorous acid

What are the hazards associated with oxone

oxidizing agent

What should be done to prevent the hazards associated with oxone

cap the vial immediately

What are the hazards associated with ethyl acetate

flammable organic solvent

What are the hazards associated with borenol and camphor

flammable solids, camphor can sublime when heated under vacuumW

What is done to prevent camphor from subliming when heating under vacuum

don’t heat water bath

What is the wittig reaction used for

contructing carbon-carbon double bonds

What is the wittig reaction

reaction of phosphonium ylide with an aldehyde or ketone to create a new alkene

What is a compound that has adjacent atoms with complete octets but opposite charges

a ylide

What type of ylide is being used in the wittig lab

pre-formed

What typically has to be done with ylides

generated in solution immediately before use by reacting the corresponding alkylphosphonium salt with a strong base

What is the wittig reaction in lab, usually run without

solvent

What do typical reactions rely on the solvent for

disperse the reaction, attenuate reactivity, control temperature

At what state does the wittig reaction occur in

molten state

What is the byproduct of the wittig reaction

triphenylphosphine oxide

What is used to get rid of the triphenylphosphine oxide in the wittig reaction

titurate (rub/grind) reaction mixture with nonpolar solvent such as hexanes

What can be done with the triphenylphosphine oxide after triturating

changed from a gum or oil to a solid that can be removed by filtration

What are the hazards associated with hexanes and methanol

flammable liquids

What are the hazards associated with triphenylphosphorane (the ylide)

toxic if ingested

What is a common way to prepare simple esters

reacting an alcohol with a carboxylic acid in the prescence of an acid catalyst

What is the common way to prepare simple esters referred to as

Fischer esterfication

What is the purpose of the acid catalyst in Fischer esterfication

activate the carbonyl to nucleophilic attach and convert a hydroxyl into a better leaving group

Why is Le Chatelier’s principle often applied to Fischer esterfication reactions

drive reaction in the forward or reverse direction

What are ways to drive the fischer esterfication formation forward

use one of the reactants in large excess or physically/chemically remove water