Alcohols phenols ethers Flashcards
The bond angle in alcohols is slightly ____ than tetrahedral angle
less - due to repulsion between unshared electrons of oxygen
The bond angle in ethers is slightly ____ than tetrahedral angle
more - repulsive interaction between bulky R groups
How are alcohols prepared from alkenes
- acid catalysed hydration - alkenes react with water in presence of acid as a catalyst. MKR
- hydroboration oxidation - diborane + alkenes give trialkyl borane which on reaction with hydrogen peroxide in the presence of aq NaOH gives alcohol. AMKR
How are alcohols prepared from carbonyl compounds?
- Reduction of aldehydes and ketones - addition of H2 in presence of catalyst - Pd Pt Ni NaBH4 LiAlH4
- Reduction of carboxylic acid - reduced to primary alcohol with excellent yield by LiAlH4
How are alcohols prepared from acids commercially
Converting to esters by adding R’OH in acid presence and then converting ester to alcohol by catalytic hydrogenation. (H in presence of catalyst)
What type of alcohol do aldehyde and ketone give on reduction?
Primary alcohol - aldehyde
Secondary alcohol - Ketone
What is the reaction mechanism from prep from Grignard reagent
Nucleophilic addition. hydrolysis
What type of alcohols are produced when we use Grignards reagent to prepare them
primary alcohol - methanal
secondary alcohol - aldehydes
tertiary alcohol - ketones
what is another name for phenol
carbolic acid
Name the 4 methods that can be used to prepare phenol in the lab
From haloarenes, From benzene sulphonic acid, From diazonium salts, From cumene
How to prep phenol from chlorobenzene
Chlorobenzene fused with NaOH at 623K and 320 atm gives sodium phenoxide. On acidification with HCl gives phenol
How to prep from benzene sulphonic acid
Benzene is sulphonated with oleum and benzene sulphonic acid so formed is converted to sodium phenoxide on heating with molten sodium hydroxide. Acidification of sodium salt gives phenol.
How to prep phenol from diazonium salts
amine + NaNO2 + HCl at 273-278 K gives diazonium salt. Diazonium salts are hydrolysed to phenols by warming with water or treating with dilute acids
How to prep phenol from cumene
Cumene oxidised in presence of air to cumene hydroperoxide. converted to phenol and acetone by treating with dilute acid.
cumene IUPAC name
isopropylbenzene
Why is bp of alcohols and phenols higher than other classes of compounds
intermolecular H-bonding
What id trend of solubility on alcohols and phenols
decrease with increase in size
Which bond has to break on alcohols from them to act as nucleophiles
O-H bond
why are alcohols acidic
polar nature oh o-h bond
what is the trend of acidic strength on alcohols
primary>secondary>tertiary
why are alcohols bases
presence of unshared electron pairs on oxygen
How are esters formed from alcohols and phenols
Carboxylic acid/acid anhydride: conc H2SO4, reversible, ROH +R’COOH = ROCOR’ +H20. water is removed as soon as it is formed.
Acid chloride: presence of base (pyridine) to neutralise HCl formed.
What is acetylation
introduction of acetyl group (CH3CO) in alcohols and phenols
Acetylation of salicylic acid gives what
Asprin
What is Lucas test
Tertiary halides from alcohol - turbidity immediately (white ppt)
Secondary alcohols - turbidity after a few minutes
Primary alcohol - no turbidity at room temp
How do alcohols become alkenes
dehydration in presence of protic acids (H2SO4, H3PO4) or catalysts such as anhy ZnCl2, alumina
what are the conditions under which alcohols become alkenes
ethanol - H2SO4 ,443K
2-propanol - 85% H3PO4, 440K
tertiary - 20% H3PO4, 358K
How to isolate aldehyde when prepared from alcohol
CrO3 in anhydrous medium is used as the oxidisng agent
How to get carboxylic acid directly from alcohoL
use strong oxidising agent like potassium permanganate
Reagents used when oxidising alcohol
aldehyde - PCC, ketone - CrO3
what happens when we pass vapours of primary or secondary alcohol over heated copper at 573 K
primary becomes aldehyde, secondary becomes ketone, tertiary becomes alkene
How to seperate ortho and para nitrophenol
steam distillation. o is steam volatile due to intramolecular hydrogen bonding and p is less volatile due to intermolecular hydrogen bonding
What different products are obtained when we use dil HNO3 and conc HNO3 with phenol
dil - nitophenol , conc - picric acid (2,4,6 - Trinitrophenol)
how to get better yield of picric acid
treat phenol with conc H2SO4 first to get 2,4 - disulphonic acid and then conc HNO3
What are the different products we get on treating phenol with bromine in different conditions
in solvents with low polarity like CHCl3 or CS2 and at low temp - monobromophenols
with bromine water - 2,4,6-tribromophenol as white ppt
What is kolbes reaction
when phenol is treated with NaOH it becomes phenoxide ion which is even more reactive. The ion + CO2 and acid gives 2- Hydroxybenzoic acid / salicylic acid
What is Reimer Tiemann reaction
Phenol + CHCl3 +NaOH gives intermediate benzal chloride. On treating with alkali we get salicylaldehyde
How to convert phenol to benzene
on heating with zinc dust
How to convert phenol to benzoquinone
phenol + Na2Cr2O7 and H2SO4
How to prep ethers
dehydration of alcohol-protic acid (413K for ethanol to ethoxyethane)
Williamson synthesis - alkyl halide + sodium alkoxide
what is the reaction mechanism for prep of ethers from alcohols
SN2
Why should we use primary alcohols for prep of ether
secondary and tertiary will follow SN1 rxn but elimination competes over substitution forming alkenes
Which reactant in Williamson’s synthesis should be primary
Alkyl halide should be primary else elimination will happen. It follows Sn2 mechanism. Sodium alkoxide can be tertiary
How to convert phenol to ether
Williamson’s synthesis. Add NaOH to give phenoxide ion and then add R-X
How to cleave ethers
drastic conditions with excess of H-X where x = I, Br
What ion do you get by protonating anisole
oxonium ion C6H5-O(+)H-CH3
