1435-1436 2014-2015 aldehydes and ketones 1. learning objectives chapter eight introduces carbonyl...
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1435-14362014-2015
Aldehydes and ketones
1
Learning Objectives
Chapter eight introduces carbonyl compounds and reactions that involve a nucleophilic attack at the carbonyl carbon in addition to the other topics. By the end of this chapter the student will:
Know the structural differences between aldehydes and ketonesKnow how to draw aldehydes and ketones know the common and IUPAC nomenclature of aldehydes and ketones Know the physical properties of aldehydes and ketonesKnow how to synthesize an aldehyde or a ketone from a compound without
that functionality. Know the different nucleophilic attack reactions at the carbonyl carbon and
the specific products formed in each case.
Aldehydes and ketones
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ALDEHYDES: STRUCTURE AND NOMENCLATURE General formula: RCHO or Bond line formula The polarity of C=O
The aldehyde group is always (terminal)at the end of a chain
145 Chem.
Common Nomenclature Of AldehydesCommon name of aldehydes are derived from the common name of
the correspounding acid Some aliphatic aldehydes have common names which have to be
memorized.
Formaldehyde Acetaldehyde Propionaldehyde Butyraldehyde
Aldehydes and ketones
R-C-H
O
R O R H
O
C
O
C
O
E
Nu
3
4
Some aromatic aldehydes have common names such as:
H
O
H
OOH
H3CO
IUPAC Nomenclature Select the longest continuous carbon chain that contains the H-C=O group to get the name of the parent hydrocarbon, then replace the ending e by the suffix –al The CHO group is assigned the local 1 and takes precedence over other functional groups that may present such as C=O(ketone),–OH, C=C, CΞC, ORFor cyclic aldehydes in which the –CHO group is attached to the ring, the suffix carbaldehyde is used.
Salicylaldehyde (o-Hydroxybenzaldehyde) Anisaldehyde (p-methoxybezaldehyde)
Aldehydes and ketones
4
H
O
OH
OCl
HO
Methanal Ethanal Propanal Butanal
3-Chlorobutanal 3-Hydroxypropanal 2-Butenal
Aromatic aldehydes are usually designated as derivatives of the simplest aromatic aldehyde, Benzaldehyde.
H
OH
O
H
OH
O OH
H3COO2NBenzaldehyde 2-Hydroxybenzaldehyde 4-Nitrobenzaldehyde 4-Methoxybenzaldehyde
Aldehydes and ketones
CHO
OHCis-2-Hydroxy cyclopentane carbaldehyde
5
General formula: RCOR’ (R and R’=alkyl or aryl)
Common names of ketones derived by listing the alkyl substituents attached to the
carbonyl group in alphabetical order, followed by the word ketone.
In common names carbon atoms near the carbonyl group are often designated using
Greek letters (α, ᵝ, ɣ , δ…..) beginning with carbon next the carbonyl group.
When a complex molecules contains more than one of functional groups, an order
of precedence is used to determine the name. The functional group priority order in nomenclature system is as following:
Acid and derivatives > aldehyde > ketone > alcohol > amine > alkene > alkyne > ether
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KETONES:STRUCTUR AND NOMENCLATURE
Aldehydes and ketones
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IUPAC Nomencalture :
Select the longest continuous carbon chain that contains the C=O
group to get the name of the parent hydrocarbon, then replace the ending
e by the suffix –one
The chain is numbered in such a way as give the lowest number to the
C=O group.
The prefix of oxo is used if there are higher ranking functional groups
present. 7
Aldehydes and ketones
CH3 C CH3
O
CH3 C C6H5
O
CH3 C CH=CH 2
O
H5C6 C
O
C6H5Acetone Acetophenone Benzophenone Dimethyl ketone Methyl phenyl ketone Methyl vinyl ketone Diphenyl ketone
7
C2H5 C
O O
C2H5
CHO
O
OH
Propanone Phenyl ethanone 3-Buten-2-one Diphenylmethanone
Cyclopentylpropanone 3-Ethyl-2-hydroxycyclohexanone 5-Oxohexanal
Aldehydes and ketones
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Physical Properties OF Aldehydes And Ketones The carbonyl group is polar; with a partial negative charge on oxygen atom, and
partial positive charge on carbon atom. Because the polarity of the carbonyl group, aldehydes and ketones are polar
compounds.
1) Boiling and melting points Higher melting and boiling points compared to analogous alkanes due to they
show dipole-dipole attractions.
These attractions although important, are not as strong as interactions due to hydrogen bonding as a result, the boiling points of aldehydes and ketones are higher than those of non polar alkanes, but lower than those of alcohols whose molecules are connected together by H-bonds.
C O C O
dipole-dipole attaraction
C O
O C
Aldehydes and ketones
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2) Solubility Lower aldehydes and ketones are are more soluble than alkanes
but less soluble than alcohols in aqueous media
C O
H
O
H CO
Aldehydes and ketones
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Preparation Of Aldehydes And ketones:1- Oxidation of Alcohols
Aldehydes and ketones
Cu/CH3CH2OH H3C CH
or PCC
O
CH3CH2OH H3C C-OH
O
KMnO4
Cu/CH3CHCH3 H3C C-CH3
or KMnO4
OOH
or PCC
PCC =N
, CrO3. HCl Pridinium Chloro chromate
11
2- Ozonolysis of Alkenes: results in formation of aldehydes or ketones depending on structure of the alkene used.
i) O3
ii) Zn / H2O
CH3CH2CHO + CH3CHO
i) O3
ii) Zn / H2O
O
O
Diketone
two aldehydes
1] O3
2]Zn/ H2O
A
A
A
A
OA
AO
A
A+
Aldehydes and ketones
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3- Hydration Of Alkynes
4- Friedel Crafts Acylation
N.B: -COR group is m-director and deactivating towards electrophiles
+ R
O
Cl
AlCl3 R
O
H2SO4,HgSO4C C C
H
OH
an enol unstable
C
H
H
carbonyl more stableO
H2O,
HC CHH2SO4,HgSO4H2O,
H
O
C CHH2SO4,HgSO4H2O,
O
H3C
Aldehydes and ketones
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Reactions Of Aldehydes And Ketonesthe most common reactions are :Nucleophilic addition reactions
1- Reduction : Formation Of Alcohols
Aldehydes and ketones
H
O
O
NaBH4
or LiAlH4
or H2 / Pd
NaBH4
or LiAlH4
or H2 / Pd
OH
OH
The reduction by NaBH4 , LiAlH4 ; the hydride ion H- is serve as nucleophile.
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2-Nucleophilic addition of Grignard reagent (formation of alcohols)
Addition of RMgX to formaldehyde gives 1◦ alc. Addition of RMgX to any other aldehyde gives 2◦ alc. Addition of RMgX to ketones gives 3◦ alc.
, dry ether+
2] H3O+
O CH3MgXCH3
OH1]
3- Oxidation reaction
Only aldehydes can be oxidized ketones resist oxidation
KMnO4
R
O
Hor
or K2Cr2O7Ar
O
H R
O
OHor
Ar
O
OH
Aldehydes and ketones
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5-Addition of Hydrogen Cyanide: Formation Of Cynohydrins
+OHO
HCN CN
+ HCN
O
H
CN
OHBenzaldehyde cyanohydrin
R+ HCN
O
R'R
OH
R'
CNcyanohydrin
Aldehydes and ketones
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6- Addition Of Alcohols:
Aldehydes and ketones
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7- Addition of Ammonia and Ammonia Derivatives
145 Chem.
H3C
O
H
Aldehyde
NH2NH2
PhNHNH2
NH2OH
NH3
H3C
N
H
NH2
hydrazone
H3C
N
H
NHPh
phenylhydrazone
H3C
N
H
OH
Oxime
H3C
NH
H imine
Aldehydes and ketones
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Exercises
1- The correct name of the following compound is: H
O
OHA) 3-hydroxyhexanalB) 3-hydroxy-4-hexenalC) 4-hydroxy-5-hexenalD)3-hydroxy-1-hexenal
2- The structure of Acetal is:
OC2H5
OH
OC2H5
OH
OH
OC2H5
OC2H5
OC2H5
OC2H5
A) B)
C) D)H
145 Chem.19
Aldehydes and ketones
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145 Chem.20
3- Reaction of phenyhydrazine with carbonyl compounds (aldyhydes or ketones) gives:
A) Oxime B) Phenylhydrazone C) Imine D) Hemiacetal
4 - Which of the following compounds has the highest boiling point?
O
H
O OH OCH3A) B) C) D)
Aldehydes and ketones
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Thank You for your kind attention !
Questions?
Comments
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Aldehydes and ketones
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