aldehyde Flashcards
what is the strcture of aldehyde
trigonal coplanar
carbonyl carbon is
and carbonyl oxygen is
electrophile (lewis acid)
nucleaophile (lewis base)
method suitable for volatile alcohol and is of industrial application
dehydrogentaion of alcohols
vapours of 1o and 2o are passed over heavy metal catalysts like CU/ Ag
ozonolysis of alkene
C=C +(i)O3 /(ii)Zn dust/ h20-> aldehyde or ketone
acids used in acid catalysed hydration af alkyne
hgso4 and h2so4
totomerise
rosenmund
chlorine chetayi mund PD H BARUNNU
CHROMYL CHLORIDE oxidation of methyl benzene
CrO2Cl2
AR-CHO
StepHen ReduCtioN
STANNOUS CHLORIDE
R-CN +SnCl2 +HCl-> RCH=NH(imine)
- H3O+ -> RCHO
eTard reaCtiO2n
cs2
toulene+ cro2cl2 in CS2-> chromium complex then acid hydrolysis-> AR-CHO
comercial preparation of BENZALDEHYDE
SIDE CHAIN CLORINATION + hydrolysis at 373K
subsituteted toulene is coverted to AR-CHO by
chromic oxide (cro3)
toulene + cro3+ acetic anhydride heatrtt-> benzylidene diacetate
acid hydrolysis + heeeat
AR-CHO
GATTERMAN KOCH
ben + CO. HCl / anh ALCl3 or cucl-> AR-CHO
prepare ketones from:
1. acyl chloride
2. nitrile
3. benzene
- acyl chloride
CDCl2 + 2RMgX -> R2Cd
* 2RCOCl + R2Cd-> 2 ketone + CdCl2 - RCN
* RCN + RMgX (ether)then acid hydrolysis - BEN
friedel crafts acylation
r/Ar -c=o cl in presence of anhydrous alcl3
higer bp of in aldehyde is due to
dipole dipole interaction which arises weak molecular ass
Arrange the following compounds in increasing order of their boiling points: CH3CHO, CH3CH2OH, CH3OCH3, CH3CH2CH3, CH3COCH3
- ch3ch2ch3
- ch30ch3
- ch3oh
- ch3coch3
- ch3ch2oh
the intermediste formed by nu- addition reaction of RCHO and RCOR’ i s>
tetrahedrasl alkoxide
aldehydes are more reactive toward NU +Rnx why?
- steric
- electronic
- the presence of 2 bulky alkyl grp hinders the approach of nu- to carbonyl carbon
- presence of 2 alkyl group reduces the electrophililitcutof the carbonyl carbonmore effect than in aldehyde
is benzaldehyde more reactive toward nucleophilic substitution reaction than propanal
In benzaldehyde, the polarity of carbonyl group decreases due to resonance. so carbon isless electrophilic
so it is less reactive than propanal
ald and ket react with HCN TO GIVE
what to do when the rnx is slow
cyanohydrins
it is catalysed by a base which gives cn- (cyanide ion) which is a stronger base readily add to C
WHY IS THE equi in largely to \rhs for alde and lhs for ket
due to steric reasons
why are hydrogen sulphite adn compound useful for separation of ald and its pruification
bisulphite addition compund is water soluble and can be concerted back to carbonyl comp with dil mineral acid or alkali
hemi acetal
alkoxy alcohol
acetal
gem diaalkoxy
ethylene glycol ketal
ketone + ethylene glycol- HCL gas and dil. HCl-> ethylene glycol ketal
why is dry hydrogen chloride used in adition of alcohol to aldehyde an dketone
What is the main function of dry HCl in the reaction?
Dry hydrogen chloride protonates the oxygen of the carbonyl compounds and therefore, increases the electrophilicity of the carbonyl carbon facilitating the nucleophilic attack of ethylene glycol
ACETALS AND KETALS are hydrolysed with aq mineral acid to form
aldehy de adn keto
hydroxylamine
NH2-OH
SCHIFFS BASE
substituted imine
c=nR
oxime
addition of hydroxylamine
C=N-OH
nh2nh2
hydrazine
what is useful for characterising ald an dket
2,4 dnp
dinitrophenylhydrazone
reduction of ald and ket by zinc amalgam and HCLis
clemmenson reduction
reduction of ald and ket by HYDRAZINE followed by HEAT WITH KOH/NAOH in high bp solvent like ethylene glycol
WOLF KISHNER REDUCTION
tollens test
reagent
detects
occurs in
SILVER MIRROR PRODUCED BY ALDE DUE TO FORMATION OF SILVER METAL
ammoniacla silver nitrate 2[Ag(NH3)2]+ warm with
ALDEHYDE
alkaline med - 3OH-
fehlings test
reagent
detects
medium
heat ald with feh reag -> reddish brown ppt due to formation od Cu2O
1.soln a- aq cu2so4
2.soln b- alkaline sodium pottasium tartarate (rochelle salt)
aldhyde (XXXaromatic aldehyde)
alkanie - 5OH-
IODOFORM TEST
detects
reagent
does it affect C=C
does it detect CH3CH(OH) then why??
ch3-c=o + naOX(sodium hypoiodite)-> sodiun salt of RCOOH with one less carbon
methyl ketone
NaO I
it doesnt affect
yes cause ch3ch(oh)produces ch3 co on oxidation
why is alpha H acidic
strong electron withdrawinf effect of carbonyl grpand resonance stabilisation gof conjugate base
CANNIZARO RNX
HCHO AND BECHO basically COOK in ROH
WHEN COOKING HEAT NEEDED
for ESR aromatic alde and keton + HNO3/H2SO3
273-283K
mNitrobenzaldehyde
cause ALDE AND KET meta directionf and deactivaitng
NUMENCLATURE
HOOC-COOH🐂
HOOC-CH2-COOH
- ETHANEDIOIC ACID
- PROPANEDIOIC ACID
JONES REAGENT
CRO3- H2SO4
TEST TO SHOW RCOOH IS MORE ACIDIC THAN PHENOLS
Sodium hydrogen carbonate
NaHCO3
STRONGEST RCOOH
TRIFLUOROACETIC ACID
ACIDS OF pKa <1
strong acids
pKa ~ 1 and 5
moderately strong
pka>15
very weak
pka ~ 5 to 15
weak
why is RCOOH more acidic tha phenol
- the carboxylate ion, the conjugate base of a carboxylic acid is s**tabilized by two equivalent resonance structures **in which the negative charge is effectively delocalized between two more electronegative oxygen atoms.
- in phenoside ion , the conjugat base is stabilised by 2 non equivalent resonance str
- negative charge is less effectively delocalized over one oxygen atom and less electronegative carbon atoms in phenoxide ion.
- Therefore, the carboxylate ion exhibits higher stability in comparison to phenoxide ion and are more acidic
how does electron withdrawing group increase the acidity of RCOOh
by delocalizing the charge of the carboxylate ion.by inductive or resonance effect
EDG DESTABILISES CARBOXYLATE
AND WEAKENS ACID
RCOOH doesnt undero FCA
bcz carboxyl group is deactivating and the lewis acid alcl3 gets bonded to carboxyl grp
DIRECT ATTACHment of phenyl or vinyl to RCOOH increases the acidity
greater electronegativity of sp2 hybridised c of RCOOH
