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13 Nuclear Magnetic Resonance Spectroscopy -- Part 4
Simple precautions may be taken to avoid an explosion.
Buying ethers should be done in small quantities and kept in tightly sealed containers.
The only ether that should be used in any procedure is peroxidefree ether.
If ether is contaminated with peroxides, it should be discarded or destroyed.
The chemistry of ethers is similar to that of thiols, except that thiols can undergo oxidation and alkylation of the sulfur atom.
Silyl ethers have some of the same properties as ethers, but they are more easily formed.
Silyl ethers are frequently used to protect alcohols.
The smell of dimethyl sulfide is similar to oysters that have been kept in the refrigerator for too long.
"sulfide" replaces "ether" in the common names for sphinxes.
The synthesis of ethers, Epoxides, and Thioethers can be done with the use of a thiolate ion.
Thiols are more acidic than water.
It is easy to generate thiol ion by treating them with a liquid.
Sulfur is larger and more polarizable than oxygen, so it's even better as a nucleophile.
Secondary alkyl halides react to give good yields when they react to Thiolates.
Sulfurs are more reactive than ethers.
Sulfur can form bonds with other atoms in a sulfide.
Sulfur forms strong bonds with oxygen, and sulfides can be easily converted to sulfoxides and sulfones.
The hydrogen peroxide/acetic acid combination is a good oxidizer.
One equivalent of peroxide oxidizes the sulfone.
The reagent combination probably reacts via the peroxyacid, which is formed in equilibrium with hydrogen peroxide.
Mild reducing agents like sulfides are often used because they are easy to oxidize.
dimethyl sulfide has been used to reduce the potentially explosive ozonides that result from ozonolysis of alkenes.
Sulfur compounds are more nucleophilic than oxygen compounds because sulfur is larger and more polarizable and its electrons are less tightly held in orbitals that are farther from the nucleus.
Although ethers are weak, sulfides are strong.
The salts are strong alkylating agents.
The carbon atom is polarized by the sulfonium salt.
An excellent leaving group is the one that expels an un charged sulfide after an attack by a nucleophile.
Sulfur lowers its energy in the transition state.
There are many alkylating agents in biological systems.
The SAM converts norepinephrine toadrenaline in the body.
The sulfur mustards were used in World War I. Nitrogen mustards are less toxic due to their ability to alkylate and alkylating agents on important metabolisms.
There is a mechanism to explain why mustard gas is so potent.
The cells are killed by inacti, a strong oxidizing agent.
Bleach is effective on organic stains because it oxidizes colored compounds to colorless compounds.
If we have a compound with two or more functional groups, and we want to modify one of them, we need to protect the other functional groups.
The alcohol group would cause the reaction to fail if we added a Grignard reagent to the carbonyl group.
Alcohol functional groups react with acids, bases, and oxidizing agents.
If alcohols are to survive a reaction at another functional group on the molecule, they must be protected.
To regenerate the original functional group, a good protecting group must be easy to remove.
We would need to convert the hydroxy group to something that is resistant to Grignard reagents to accomplish the reaction shown above.
An ether might be used to protect a group in a Grignard reaction.
It can be difficult to remove an ether protecting group.
It requires strong acid to react with the free hydroxy group.
Silyl ethers are easier to remove than carbon ethers.
Under gentle conditions, the fluoride ion can remove silyl ethers.
Synthetic organic chemists have developed many different silyl protecting groups that vary in reactivity and are carefully chosen for a specific use.
The three bulky isopropyl groups help keep the silyl ether stable.
Silyl ethers are formed by the reaction of alcohols with chlorosilanes.
chlorotriisopropylsilane can be reacted with a tertiary amine to form TIPS ether.
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