Organic II - Ether, Epoxides and Thioethers Flashcards
Give formula for an ether.
R-O-R’
Are ethers symmetrical or unsymmetrical?
Both.
What is the structure and polarity of ethers? (hybridization, molecular geometry, angle and polarity)
O is sp3 hybridized, bent molecular geometry, C-O-C 110 degrees and polar C-O bond
Boiling point of ethers are similar to _______.
alkanes
Can ethers hydrogen bond with other molecules?
No
Ethers have a lower b.p than ________.
alcohols
Ether molecules can H bond with ______ & ________ molecules.
water; alcohol
Why are ethers used as solvents?
They can dissolve n.p and polar substances and are unreactive with strong bases.
-OCH3 is named as…
methoxy
Give the epoxide formula.
CH2-O-CH2
Define heterocyclic.
O is part of the ring
Oxetane is…
O + 3 C ring (forms a square)
Dioxane is…
2 O + 4 C (hexagon)
Furan is…
O + 4 C with 2 double bonds (dicyclopentene)
Pyran is…
O + 5 C with 2 double bonds (dicyclohexene)
Name all the heterocycles.
epoxide, oxetane, furan, pyran, dioxane
Another name for oxirane is…
1,2-epoxyethane
What method does the preparation of ether use?
Williamson ether synthesis
What are two common products of nucleophilic substitution?
Alcohols and ethers
Can unsymmetrical ethers be synthesized two different ways?
Yes.
Which path is preferred in Williamson ether synthesis?
Alkoxide attack less hindered alkyl halide.
Why are phenoxide ions easily produced?
The alcohol proton is acidic.
Phenyl halides or tosylates can’t be used in Williamson ether synthesis because…
They are poor substrates.
MCPBA with a double bond usually forms…
an epoxide
Formation of the chlorohydrin involves what? (reactant, intermediate, product)
alkene, chloronium ion, chlorohydrin enantiomers
What are the reactants of the formation of chlorohydrin?
Cl2 and H2O
What are the reactants of the displacement of chlorohydrin?
Base like OH-
What does the displacement of chlorohydrin produce?
Epoxide, H2O and Cl- ion
In base-catalyzed opening of epoxide, the base attacks the __________ carbon.
less substituted
Opening an epoxide ring with HCl, Cl- attacks the ___________ carbon.
more substituted
Define regioselectivity.
Ring opening of an epoxide with either a strong nucleophile or an acid (HZ)
When opening an epoxide with a strong nucleophile, it attacks the ____ substituted carbon.
less
When opening an epoxide with an acid, it attacks the ____ substituted carbon.
more
Grignards and organolithiums open an epoxide ring by attacking the _____ hindered carbon.
less
A primary alcohol reacting with H2SO4 and heat produces…
An ether and H2O
Does a secondary alcohol (alkane) reacting with H2SO4 and heat produce an ether?
No. (Alkene with H2O)
How to convert a poor leaving group to a good one on ethers?
Reaction with strong acids (ex. HBr and HI)
What happens to the C-O bond of ethers reacting with HBr or HI?
C-O bonds are cleaved & 2 alkyl halides are formed.
A branched structure (tertiary C-O bond) goes through _____ mechanism when cleaved.
SN1
CH3-OH bond goes through ___ mechanism when cleaved.
SN2
Phenyl ether cleavage produces what?
Phenol and an alkyl halide
Give the standard formula for thioethers.
R-S-R’
Name CH3-S-CH3.
Dimethyl sulfide
Are thioethers easily synthesized by the Williamson ether synthesis?
Yes.
_________ ion is used as the nucleophile in the synthesis of thioethers.
Thiolate
