Transcript Chapter 15 Aldehydes and Ketones

Chapter 15
Aldehydes and Ketones
Milbank High School
Objectives/Study Questions
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1.What is the general structure for an aldehyde?
A ketone?
2.How are the common names of aldehydes and
ketones determined? How are aldehydes and
ketones named using IUPAC nomenclature?
3.Why are the boiling points of aldehydes and
ketones higher than those of ethers and alkanes
of similar molar masses, but lower than those of
comparable alcohols?
Objectives/Study Questions
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4.How do the solubilities of aldehydes and
ketones of four carbons or less compare to the
solubilities of comparable alkanes and alcohols
in water?
5.How are aldehydes and ketones prepared?
6.What typical reactions take place with
aldehydes and ketones?
7.What are some common aldehydes and
ketones and their uses?
Carbonyl Group
Carbon atom joined to oxygen by a double
bond
 Ketones
 Aldehydes
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Aldehydes
Comes from alcohol dehydrogenation
 Obtained by removing of a hydrogen from
an alcohol
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Aldehydes
Both common and IUPAC names
frequently used
 Common names from acids from which
aldehydes can be converted
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Aldehydes
IUPAC
 Longest chain with aldehyde
 Drop “e” and add “-al”
 Aldehyde takes precedence over all other
groups so far
 Examples
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Ketones
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Naming:
Drop “e”, add “-one”
 Many common names
 Simplest is 3 carbons
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 C.
name: acetone
 IUPAC: propanone
Ketones
Carbonyl carbon gets lowest number
 See examples…
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Common Carbonyl Compounds
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Formaldehyde
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Acetaldehyde
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Prepared from ethyl alcohol
Formed in the detoxification of alcohol in the liver
Acetone
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Manufactured from methanol
Used in many polymers
Formed in the human body as a by-product of lipid
metabolism
Excreted in the urine
Hormones
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Steroid hormones
Progesterone/Testosterone
Physical Properties of Aldehydes
and Ketones
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Carbon-oxygen double bond is very polar
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Odors
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Affects boiling points
More than ethers (C-O bonds)
Less than alcohols (C-OH bonds)
Low aldehydes very pungent
High aldehydes pleasant odors (perfumes)
Solubility
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Similar to alcohols and ethers
Soluble up to about 4 carbons
Insoluble after that
Preparation of Aldehydes
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Oxidation
Leads to carboxylic acid unless care is taken
 1° alcohols
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Preparation of Ketones
Oxidation of a 2° alcohol
 Utilizes chromium compounds and sulfuric
acid
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Chemical Properties of Aldehydes
and Ketones
Both under-go combustion reactions
 Oxidation
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Aldehydes can be oxidized, ketones can’t
 See Pg 403
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 Tollen’s
reagent
 Benedict’s reagent
 Fehling’s reagent
Chemical Properties of Aldehydes
and Ketones
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Reduction
Variety of agents can reduce aldehydes and
ketones to alcohols
 NaBH4 and H2 commonly used
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Chemical Properties of Aldehydes
and Ketones
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Hydration
Formaldehyde dissolves readily in water
 Acetaldehyde somewhat also
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 Form
hydrates
Chemical Properties of Aldehydes
and Ketones
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Addition of Alcohols to Carbonyl Groups
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Hemiacetal
 Aldehyde
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+ alcohol
Hemiketal
 Ketone
+ alcohol
Not very stable
 Differs from
1 mol to 2 mol
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Chemical Properties of Aldehydes
and Ketones
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Hemiacetals + HCl = acetal
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Hemiketal + HCl = ketal