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Chapter 9Ketones and Aldehydes
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Carbonyl Compounds
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Carbonyl StructureCarbon is sp2 hybridized.C=O bond is shorter,
stronger, and more polar than C=C bond in alkenes.
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Chapter 9*IUPAC Names for KetonesReplace -e with -one. Indicate
the position of the carbonyl with a number.Number the chain so that
carbonyl carbon has the lowest number.For cyclic ketones the
carbonyl carbon is assigned the number 1.
Chapter 9
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Chapter
9*Examples3-methyl-2-butanone3-methylbutan-2-one3-bromocyclohexanone4-hydroxy-3-methyl-2-butanone4-hydroxy-3-methylbutan-2-one
Chapter 9
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Chapter 9*Naming AldehydesIUPAC: Replace -e with -al.The
aldehyde carbon is number 1.If -CHO is attached to a ring, use the
suffix -carbaldehyde.
Chapter 9
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Chapter
9*Examples3-methylpentanal2-cyclopentenecarbaldehydecyclopent-2-en-1-carbaldehyde
Chapter 9
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Chapter 9*Name as SubstituentOn a molecule with a higher
priority functional group, C=O is oxo- and -CHO is formyl.Aldehyde
priority is higher than
ketone.3-methyl-4-oxopentanal3-formylbenzoic acid
Chapter 9
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Chapter 9*Common Names for KetonesNamed as alkyl attachments to
-C=O.Use Greek letters instead of numbers.methyl isopropyl
ketonea-bromoethyl isopropyl ketone
Chapter 9
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Chapter 9*Historical Common
Namesacetoneacetophenonebenzophenone
Chapter 9
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Chapter 9*Aldehyde Common NamesUse the common name of the
acid.Drop -ic acid and add -aldehyde.1 C: formic acid,
formaldehyde2 Cs: acetic acid, acetaldehyde3 Cs: propionic acid,
propionaldehyde4 Cs: butyric acid, butyraldehyde.5 Cs: valeric
acid, valeraldehyde
-bromobutyraldehyde 3-bromobutanal
Chapter 9
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Chapter 9*Boiling PointsMore polar, so higher boiling point than
comparable alkane or ether.Cannot H-bond to each other, so lower
boiling point than comparable alcohol.
Chapter 9
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Chapter 9*SolubilityGood solvent for alcohols.Lone pair of
electrons on oxygen of carbonyl can accept a hydrogen bond from O-H
or N-H.Acetone and acetaldehyde are miscible in water.
Chapter 9
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Chapter 9*FormaldehydeGas at room temperature.Formalin is a 40%
aqueous solution.
Chapter 9
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Chapter 9*Industrial ImportanceAcetone and methyl ethyl ketone
are important solvents.Formaldehyde used in polymers like
Bakelite.Flavorings and additives like vanilla, cinnamon,
artificial butter.
Chapter 9
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Chapter 9*Synthesis ReviewOxidation2 alcohol + Na2Cr2O7 ketone1
alcohol + PCC aldehydeOzonolysis of alkenes.
Chapter 9
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Chapter 9*Synthesis Review (2)Friedel-Crafts acylationAcid
chloride/AlCl3 + benzene ketoneHydration of terminal alkyneUse
HgSO4, H2SO4, H2O for methyl ketone
Chapter 9
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Chapter 9*Aldehydes from Acid ChloridesUse a mild reducing agent
to prevent reduction to primary alcohol.
Chapter 9
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Chapter 9*Ketones from Acid ChloridesUse lithium dialkylcuprate
(R2CuLi), formed by the reaction of 2 moles of R-Li with cuprous
iodide.
Chapter 9
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Chapter 18*Nucleophilic AdditionA strong nucleophile attacks the
carbonyl carbon, forming an alkoxide ion that is then protonated.A
weak nucleophile will attack a carbonyl if it has been protonated,
thus increasing its reactivity.Aldehydes are more reactive than
ketones.
Chapter 18
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Chapter 9*Addition of WaterIn acid, water is the nucleophile.In
base, hydroxide is the nucleophile.Aldehydes are more electrophilic
since they have fewer e--donating alkyl groups.a gemdiola
gemdiol
Chapter 9
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Chapter 9*Addition of Alcohol
Chapter 9
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Chapter 9*MechanismMust be acid-catalyzed.Adding H+ to carbonyl
makes it more reactive with weak nucleophile, ROH.Hemiacetal forms
first, then acid-catalyzed loss of water, then addition of second
molecule of ROH forms acetal.All steps are reversible.
Chapter 9
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Chapter 9*Mechanism for HemiacetalOxygen is protonated.Alcohol
is the nucleophile.H+ is removed. =>
Chapter 9
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Chapter 9*Hemiacetal to Acetal
Chapter 9
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Chapter 18*Oxidation of AldehydesEasily oxidized to carboxylic
acids.
Chapter 18
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Chapter 9*Cyclic AcetalsAddition of a diol produces a cyclic
acetal.Sugars commonly exist as acetals or hemiacetals.
Chapter 9
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Chapter 18*Tollens TestAdd ammonia solution to AgNO3 solution
until precipitate dissolves.Aldehyde reaction forms a silver
mirror.
Chapter 18
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SILVER MIRROR
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Chapter 18*Reduction ReagentsSodium borohydride, NaBH4, reduces
C=O, but not C=C.Lithium aluminum hydride, LiAlH4, much stronger,
difficult to handle.Hydrogen gas with catalyst also reduces the C=C
bond.
Chapter 18
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Chapter 18*Catalytic HydrogenationWidely used in industry.Raney
nickel, finely divided Ni powder saturated with hydrogen gas.Pt and
Rh also used as catalysts.
Chapter 18
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TautormersConstitutional isomers in equilibrium with each other
that differ in the location of a hydrogen atom and a double bond
are called tautomers.A case of tautomerization occurs with ketones
(aldehydes) that are in equilibrium with their enol form, which are
called keto enol tautomers
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ALDEHYDE AND KETONE REVIEW
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Name a. Cis-2-pentenalb. Cis-2-pentanalc. Trans-2-pentenald.
Trans-2-pentanal
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Answera. Cis-2-pentenalb. Cis-2-pentanalc. Trans-2-pentenald.
Trans-2-pentanal
The aldehyde is in position one. The double bond is trans.
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Name a.2-Oxobutanoic
acidb.2-Butanone-1-carbaldehydec.2-Oxopentanoic
acidd.3-Oxopentanoic acid
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Answera.2-Oxobutanoic
acidb.2-Butanone-1-carbaldehydec.2-Oxopentanoic
acidd.3-Oxopentanoic acid
The carbon in the carboxylic acid is position one.
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Identify the chemical name for
acetone.a.Methanalb.Ethanalc.Propanoned.Butanone
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Answera.Methanalb.Ethanalc.Propanoned.Butanone
Acetone is called propanone or dimethyl ketone.
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a.2-Propanoneb.2-Butanonec.2-Pentanoned.3-Pentanone
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Answera.2-Propanoneb.2-Butanonec.2-Pentanoned.3-Pentanone
2-Butanone is formed in the Grignard reaction. The secondary
alcohol is oxidized to a ketone with sodium dichromate.
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a.2-Propanoneb.2-Butanonec.2-Pentanoned.3-Pentanone
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Answera.2-Propanoneb.2-Butanonec.2-Pentanoned.3-Pentanone
The ethyl group adds to the carbonyl carbon.
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a.2,2-Diethoxypropaneb.2-Ethoxy-2-propanolc.Propane-2,2-diold.2-Ethoxypropane
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Answera.2,2-Diethoxypropaneb.2-Ethoxy-2-propanolc.Propane-2,2-diold.2-Ethoxypropane
Two molecules of ethanol are added to the carbonyl, with loss of
water.
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a.1-Propanolb.Propanoic
acidc.Propane-1,1-diold.1-Hydroxypropanoic acid
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Answera.1-Propanolb.Propanoic
acidc.Propane-1,1-diold.1-Hydroxypropanoic acid
The Tollens reagent reduces an aldehyde to a carboxylic
acid.
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a.2-Butanoneb.2-Butanolc.2-Hexanoned.Butane
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Answera.2-Butanoneb.2-Butanolc.2-Hexanoned.Butane
Butanone is reduced to 2-butanol.
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Chapter 9*End of Chapter 9
Chapter 9
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