Alcohols, Ethers, and Epoxides Flashcards
-OH groups are polar or nonpolar?
polar
soluble in water - important in drugs
primary alcohol (carbinol carbon atom):
C-OH wich 2H bonded to C
1Rgroup
secondary alcohol (carbinol carbon atom):
C-OH
1H bonded to Cand 2R groups
teritary alcohol (carbinol carbon atom):
C-OH with 3R groups attached to the C
Alcohols can form hydrogen bonds. Two further important properties:
- Alcohols are soluble in water
- Molecules with alcohol groups can H-bond to proteins
what are the 2 steps of Synthesis of Alcohols?
- Nucleophilic substitution on an alkyl halide
- Synthesis of alcohols from alkenes
- Addition of acetylides to carbonyl compounds (C=O)
- Synthesis of alcohols from alkenes
3 parts and product
a. Acid-catalysed hydration
b. Oxymercuration–demercuration
c. Hydroboration–oxidation
Markovnikov product»_space;> Anti-Markovnikov product
What reagent does Markovnikov need for dehydration reaction?
Boron
What reagant does Anti-Markovnikov need for dehydration reaction?
Mercury
Organometallic compounds
covalent bonds between carbon atoms and metal atoms
Nucleophilic carbon atoms > organometallic
> gets attacked by
a strong nucleophile
Most alkyl and alkenyl groups are not ______ enough to be deprotonated by NaNH2
acidic
Grignard and organolithium reagents:
strong nucleophiles/strong bases
Nucleophilic reactions are additions of what group?
carbonyl (C=O) groups
Organometallic reagents for alcohol synthesis 3 steps
1) Formation of the Grignard reagent
2) The Grignard reagent attacks a carbonyl compound to form an alkoxide salt
3) After the first reaction is complete, water/dilute acid is added to protonate the alkoxide and give the alcohol
[primary] formaldehyde when reagent attacks the C
the lone pair of e will shift to the O and form a primary alcohol
secondary aldehyde froms what type of alcohol
secondary
ketone forms what type of alcohol
tertiary (3)
Reduction of the C=O: synthesis of 1° and 2° alcohols
Reduction of the C=O: synthesis of 1° and 2° alcohols
Sodium borohydride (NaBH4)
are involved in what two processes
1) Borohydride transfers a hydride ion (H:-) to carbon, forming an alkoxide ion
2) The alcohol solvent protonates the alkoxide
What is being reduced in the second step of synthesis of 1st and 2nd alcohols and what does NOT reduce?
Reduces ketones (2˚alcohols)
Reduces aldehydes (1˚ alcohols)
Does not reduce carbonyl groups: acids, esters, and other acid derivatives
LiAlH4 v NaBH4
LiAlH4 much stronger reagent
Easily reduces ketones (2˚alcohols) and aldehydes (1˚ alcohols)
Reduces carbonyl groups (1˚ alcohols): acids, esters, and other acid derivatives
Hydride reagents add a hydride ion (H:-), reducing the C=O to an alkoxide ion
what reagent is used?
Lithium aluminium hydride (LiAlH4)
2 steps to reduction of Reduction of the C=O: synthesis of 1° and 2° alcohols using LiAlH4:
- LAH transfers a hydride ion (H:-) to carbon, forming an alkoxide ion
- After the first reaction is complete, water/dilute acid is added to protonate the alkoxide
Inorganic chemistry
oxidation/reduction is a loss/gain of electrons i.e. Cr6+to Cr3+
oxidation is
adding an oxidising agent (O, O2, Br2, etc.) or losing H2
reduction is
is adding a reducing agent (H2, NaBH4, H-etc.) or losing O, O2 or X2
neither an oxidation nor a reduction: addition or loss of…
H+, -OH, H2O, HX, etc.
oxidation usually converts C-H bonds to
C-O bonds
name the 3 steps of Oxidation of alcohols:
- Oxidation of primary alcohols to carboxylic acids
- Oxidation of primary alcohols to aldehydes
- Oxidation of secondary alcohols to ketones
Why is it important for our bodies to detoxify alcohol?
keep it from building up in blood and poisoning the brain
ethanol - 1 alcohol is transformed to
acetaldehyde
methanol > formaldehyde >
formic acid
a weak nucleophile (alcohol) will attack the strong electrophile. what will happen to the charge on the oxygen?
the +ive charge will move from the C to the O
O will start with 2 lone pairs and then end up with only one because one is taken up by H and the other by the C that had been attacked by the nucleophile
what do we add to a weak nucleophile to make a strong nucleophile?
Na
this will break the bond between the O-H, H will leave the O and leave O with 3 lone pairs with a -ive charge
alcohols - strong nucleophile = lone pair from O will attack the C in the ____ ________
weak electrophile which will attach the the alcohol (weak nucleophile)
how to turn poor electrophile to a good electrophile?
add HBr as the extra H will attach to the oxygen taking up the lone pair and leaving a +ive charge
Br- will be by itself
BETTER LEAVING GROUP (ACTIVATE THE OH)
Convert –OH to a better tosylate leaving group
step 1 and 2
Step 1: Activation to tosylate
Step 2: SN2 displacement of tosylate ion (-OTs)
In 2 steps, an alcohol is transformed to a different functional group through a
SN2 reaction
in an SN reaction should R group be hindered or unhindered?
R must be an unhindered primary or secondary alkyl group if substitution is to predominate over elimination
n
in the conversion of alcohols to alkyl halides what reaction is teritary and secondary?
what about primary?
SN1
SN2
how to form ethers?
bimolecular condensation
reaction that joins two (or more) molecules, often with the loss of a small molecule such as water
acidic dehydration conditions two reactions compete:
A) Elimination, dehydration to give an alkene
B) Substitution, condensation to give an ether
What do we call forming an ester in alcohols?
Esterification of alcohols
explain esterification of alcohols
Replacing the -OH group of a carboxylic acid with the -OR group of an alcohol
Inorganic esters
the alkoxy ( -OR) group replaces a –OH of an inorganic acid
The Williamson ether synthesis
Alkoxide ion reacts with primary alkyl halides and tosylates to form ethe
ether synthesis = if alkyl halide is hindered?
what process will happen
elimination
what are ethers?
O-R’.
R may be alkyl group or aryl group
[aryl - functional group derived from an aromatic]
Most common methods for ethers preparation:
Williamson synthesis and bimolecular condensation of alcohols
- Peroxyacid epoxidation
Opening of epoxide: 1. Acid-Catalysed
a. In water to form glycols
b. In alcohols to form an alkoxy alcohol
c. Using hydrohalic acids
b. In alcohols to form an alkoxy alcohol
Protonation of oxygen (forming a good leaving group), followed by the alcohol attack as if it were an ….
SN1-type reaction The alkoxy group bonds to the more highly substituted carbon
a. In water to form glycols
Protonation of oxygen (forming a good leaving group), followed by….
SN2 attack by water
second part of opening of epoxide
- Base-catalysed
a. with alkoxides or hydroxide [The alkoxide ion simply attacks the less hindered carbon atom in an SN2 displacement]
b. with organmetallics [Carbanion usually attacking the less hindered epoxide carbon atom:
R bonds to the less substituted carbon]
