Chapter 15 Aldehydes.ppt

Chapter 15Chapter 15Aldehydes and KetonesAldehydes and Ketones

Milbank High SchoolMilbank High School

Objectives/Study QuestionsObjectives/Study Questions

1.1.What is the general structure for an aldehyde? What is the general structure for an aldehyde? A ketone?A ketone?

2.2.How are the common names of aldehydes and How are the common names of aldehydes and ketones determined? How are aldehydes and ketones determined? How are aldehydes and ketones named using IUPAC nomenclature?ketones named using IUPAC nomenclature?

3.3.Why are the boiling points of aldehydes and Why are the boiling points of aldehydes and ketones higher than those of ethers and alkanes ketones higher than those of ethers and alkanes of similar molar masses, but lower than those of of similar molar masses, but lower than those of comparable alcohols?comparable alcohols?

Objectives/Study QuestionsObjectives/Study Questions

4.4.How do the solubilities of aldehydes and How do the solubilities of aldehydes and ketones of four carbons or less compare to the ketones of four carbons or less compare to the solubilities of comparable alkanes and alcohols solubilities of comparable alkanes and alcohols in water?in water?

5.5.How are aldehydes and ketones prepared?How are aldehydes and ketones prepared? 6.6.What typical reactions take place with What typical reactions take place with

aldehydes and ketones?aldehydes and ketones? 7.7.What are some common aldehydes and What are some common aldehydes and

ketones and their uses?ketones and their uses?

Carbonyl GroupCarbonyl Group

Carbon atom joined to oxygen by a double Carbon atom joined to oxygen by a double bondbond

KetonesKetonesAldehydesAldehydes

AldehydesAldehydes

Comes from Comes from alalcohol cohol dehyddehydrogenationrogenationObtained by removing of a hydrogen from Obtained by removing of a hydrogen from

an alcoholan alcohol

Aldehydes Aldehydes

Both common and IUPAC names Both common and IUPAC names frequently usedfrequently used

Common names from acids from which Common names from acids from which aldehydes can be convertedaldehydes can be converted

AldehydesAldehydes

IUPACIUPACLongest chain with aldehydeLongest chain with aldehydeDrop “e” and add “-al”Drop “e” and add “-al”Aldehyde takes precedence over all other Aldehyde takes precedence over all other

groups so fargroups so farExamplesExamples

KetonesKetones

Naming:Naming:Drop “e”, add “-one”Drop “e”, add “-one”Many common namesMany common namesSimplest is 3 carbons Simplest is 3 carbons

C. name: acetoneC. name: acetoneIUPAC: propanoneIUPAC: propanone

KetonesKetones

Carbonyl carbon gets lowest numberCarbonyl carbon gets lowest numberSee examples…See examples…

Common Carbonyl CompoundsCommon Carbonyl Compounds FormaldehydeFormaldehyde

Manufactured from methanolManufactured from methanol Used in many polymersUsed in many polymers

AcetaldehydeAcetaldehyde Prepared from ethyl alcoholPrepared from ethyl alcohol Formed in the detoxification of alcohol in the liverFormed in the detoxification of alcohol in the liver

AcetoneAcetone Formed in the human body as a by-product of lipid Formed in the human body as a by-product of lipid

metabolismmetabolism Excreted in the urineExcreted in the urine

HormonesHormones Steroid hormonesSteroid hormones Progesterone/TestosteroneProgesterone/Testosterone

Physical Properties of Aldehydes Physical Properties of Aldehydes and Ketonesand Ketones

Carbon-oxygen double bond is very polarCarbon-oxygen double bond is very polar Affects boiling pointsAffects boiling points More than ethers (C-O bonds)More than ethers (C-O bonds) Less than alcohols (C-OH bonds)Less than alcohols (C-OH bonds)

OdorsOdors Low aldehydes very pungentLow aldehydes very pungent High aldehydes pleasant odors (perfumes)High aldehydes pleasant odors (perfumes)

Solubility Solubility Similar to alcohols and ethersSimilar to alcohols and ethers Soluble up to about 4 carbonsSoluble up to about 4 carbons Insoluble after thatInsoluble after that

Preparation of AldehydesPreparation of Aldehydes

Oxidation Oxidation Leads to carboxylic acid unless care is takenLeads to carboxylic acid unless care is taken11° alcohols° alcohols

Preparation of KetonesPreparation of Ketones

Oxidation of a 2Oxidation of a 2°° alcohol alcoholUtilizes chromium compounds and sulfuric Utilizes chromium compounds and sulfuric

acidacid

Chemical Properties of Aldehydes Chemical Properties of Aldehydes and Ketonesand Ketones

Both under-go combustion reactionsBoth under-go combustion reactionsOxidationOxidation

Aldehydes can be oxidized, ketones can’tAldehydes can be oxidized, ketones can’tSee Pg 403See Pg 403

Tollen’s reagentTollen’s reagentBenedict’s reagentBenedict’s reagentFehling’s reagentFehling’s reagent


Reduction Reduction Variety of agents can reduce aldehydes and Variety of agents can reduce aldehydes and

ketones to alcoholsketones to alcoholsNaBHNaBH4 4 and H and H2 2 commonly usedcommonly used


HydrationHydrationFormaldehyde dissolves readily in waterFormaldehyde dissolves readily in waterAcetaldehyde somewhat alsoAcetaldehyde somewhat also

Form Form hydrateshydrates


Addition of Alcohols to Carbonyl GroupsAddition of Alcohols to Carbonyl GroupsHemiacetalHemiacetal

Aldehyde + alcoholAldehyde + alcohol

Hemiketal Hemiketal Ketone + alcoholKetone + alcohol

Not very stableNot very stableDiffers from Differs from

1 mol to 2 mol1 mol to 2 mol


Hemiacetals + HCl = acetalHemiacetals + HCl = acetal

Hemiketal + HCl = ketalHemiketal + HCl = ketal

Chapter 15 Aldehydes.ppt

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