Ethers
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What are ethers? 2
A class of organic compounds containing an O atom bonded by a single bond to two alkyl and or aryl groups The two alkyl/aryl groups can be the same or different
What is the O in ethers bonded to?
To two alkyl and/or aryl groups
What type of bond is found between the O and the alkyl/aryl groups in ethers?
A single group
What is an alkyl group?
Its an alkane with a hydrogen atom missing from its chain
What is the general formula of an alkyl group?:
Cn H(2n+1)
What is the smallest alkyl group?
The methyl group (CH3)
What is an aryl group?
A simple aromatic compound with one of its hydrogen atoms missing (this missing atom allows the molecule to attach to a carbon chain)
Give an example of an aryl group.
Tolyl group (derived from toluene - a benzene ring with the substitution of a methyl group)
How are ethers named if both of their groups are alkyl groups?
The ether is usually named as alkyl aklyl ether The alkyl groups are listed in alphabetical order If the two alkyl groups are the same then it’s a dialkyl ether
Give an example of a dialkyl ether.
Dimethyl ether (an O singly bonded to two methyl groups - CH3)
When naming an ether with two alkyl groups, how do you decide the order of naming the alkyl groups?
The alkyl groups are listed in alphabetical order
How do you name an ether which has two of the same alkyl groups?
Dialkyl ether
How is an ethyl group written in an ether?
CH3 CH2
How do you go about naming intermediate ethers?
You treat the ether group as an alkoxy group The root name is defined by the more complex group i.e. longer chain
What is the formula for methoxy?
CH3O
What is the name given to CH3CH2O?
Ethoxy
What exactly is an intermediate ether?
An ether where there is one complex group
What exactly is a complex ether?
An ether where there is two complex group
How do you name a complex ether?
Ether is treated as a chain substituent and given the prefix oxa
What three factors affect boiling point? 3
Relative strength of intermolecular forces; coulombic forces > dipole forces > induced dipole forces B.p increases with increasing molecular mass i.e. number of C atoms and FGs present Molecular symmetry or lack thereof - b.p. decreases with branching
List the intermolecular forces in order of increasing strength.
Ionic > H-bonding > Dipole-dipole > induced dipole - induced dipole
What is the relationship between a compound’s molar mass and boiling point?
Boiling point increases with molecular mass i.e. the number of C atoms anf FGs present
What is the relationship between molecular symmetry and boiling point?
Boiling point decreases with branching Symmetrical molecules with no branching have higher boiling points
How do the boiling points of ethers compare to that of alcohols with an equal number of C atoms?
Ethers have lower boiling points than these alcohols