Aldehydes & Ketones

Goals for the Day…. Naming Aldehydes & Ketones Physical Properties of Aldehydes & Ketones Reactions of Aldehydes & Ketones

Aldehydes and Ketones Both contain a carbonyl group, an aldehyde has a carbonyl carbon bonded to one H atom. a ketone, has the carbonyl carbon bonded to two carbon groups.

Structural and Skeletal Formulas Aldehyde Ketone Your book might use this abbreviation, but it is not really preferred…

Learning Check Identify the following compounds as either an aldehyde or ketone. A. CH3—CH2—CH2—COH B. CH3—CH2—CO—CH2—CH2—CH3 C. D.

Solutions A. CH3—CH2—CH2—COH aldehyde B. CH3—CH2—CO—CH2—CH2—CH3 ketone C. ketone D. aldehyde

Naming Aldehydes Suffix becomes anal. has a common name for the first four aldehydes that use the prefixes: form- (1C), acet- (2C), propion- (3C), and butyr- (4C), followed by -aldehyde. Must be included in the longest chain of carbons (and is automatically carbon #1).

Your Book’s Guide to Naming Aldehydes

Learning Check: Try this in your Composition Book… Give the IUPAC name of the following aldehydes… A. CH3—CH—CH2—CH2—CHO Cl

Solution carbon 1 4- chloro pentanal (note that the carbonyl carbon is automatically carbon 1). A. CH3—CH—CH2—CH2—CHO Cl

Learning Check: Try this in your Composition Book… Give the IUPAC name of the following aldehydes.

Solution ortho ethyl benzaldehyde

Examples for you to try…

Answer… 4-butyl hexanal

Learning Check 4-Methylpentanal Draw the condensed structural formulas for the following in your composition book…. 4-Methylpentanal

Solution 4-Methylpentanal

Learning Check Draw the condensed structural formulas for the following in your composition books… 2,3-Dichloropropanal

Solution B. 2,3-Dichloropropanal Remember that the carbonyl carbon is carbon 1!  B. 2,3-Dichloropropanal

Aldehydes in Flavorings Several naturally occurring aldehydes are used as flavorings for foods and fragrances. Benzaldehyde (almonds) Cinnamaldehyde (cinnamon)

Naming Ketones The carbonyl carbon has to be included in the longest chain of carbons The carbonyl carbon gets priority in the numbering The suffix becomes -anone 2-butanone Ethyl methyl ketone Smallest possible… 2-propanone acetone

Ketones with Common Names IUPAC retains well-used but unsystematic names for a few ketones

Your Book’s Guide to Naming Ketones

Examples to try

Answer 3-butyl-2-octanone

Examples to try

Answer… 7-phenyl-2-nonanone

Learning Check 3-Methyl-2-butanone Draw the condensed structural formulas for the following. 3-Methyl-2-butanone

Solution Should look something like this… 3-Methyl-2-butanone

Ketones in Common Use Solvent: nail polish remover (acetone, propanone, dimethylketone)

Polar Carbonyl Group The polar carbonyl group provides dipole–dipole interactions. The partial positive carbon is attracted to the partial negative charge on a second carbonyl oxygen.

Boiling Points Aldehydes and ketones have dipole–dipole interactions between polar groups. higher boiling points than alkanes and ethers of similar mass due to dipole–dipole interactions. lower boiling points than alcohols of similar mass because they do not form hydrogen bonds.

Order of intermolecular forces… Hydrogen Bonding (alcohols…hydrogen bonders) Dipoles (Aldehydes and ketones…carbonyl compounds) Van der Waals (everything has these)

Comparison of Boiling Points

Ranking m.p./b.p... ________>__________>__________>__________ Highest lowest

Ranking m.p./b.p... a b d c ________>__________>__________>__________ Highest lowest

Solubility of Aldehydes and Ketones in Water with one to four carbons are soluble in water. with five or more carbons are not very soluble in water. form hydrogen bonds with water between the carbonyl oxygen and hydrogen atoms of water.

Boiling Points, Solubility of Aldehydes and Ketones

Water solubility (which will be soluble?)...

The compounds containing Oxygen & Nitrogen will be soluble in water (up to 6 carbons) Note: The alkanes & alkenes are not water soluble…

Learning Check Select the compound in each pair that would have the higher boiling point. Explain. A. An alcohol forms hydrogen bonds. B. There are dipole–dipole attractions between the carbonyl groups. C. CH3—CH2—CH3 or CH3—CH2—OH or CH3—CH2—OH or CH3—O—CH3

Solution Higher Boiling Point Reason A. CH3—CH2—OH An alcohol forms hydrogen bonds. B. There are dipole–dipole attractions between the carbonyl groups. C. CH3—CH2—OH An alcohol forms hydrogen bonds, but an ether does not. CH3—CH2—OH An alcohol forms hydrogen bonds. There are dipole–dipole attractions between the carbonyl groups. CH3—CH2—OH An alcohol forms hydrogen bonds, but an ether does not

A. CH3—CH2—CH3 B. CH3—CH2—OH C. D. Learning Check Indicate if each of the following is or is not soluble in water. A. CH3—CH2—CH3 B. CH3—CH2—OH C. D.

Solution A. CH3—CH2—CH3 B. CH3—CH2—OH C. D. not soluble in water soluble in water soluble in water soluble in water

Oxidation Alcohols are easily oxidized to aldehydes or ketones. Aldehydes are easily oxidized to carboxylic acids. Ketones cannot be oxidized.

Oxidation

Tollens’ Test Tollens’ reagent, which contains Ag+, oxidizes aldehydes but not ketones. Ag+ is reduced to metallic Ag, during oxidation. Ag appears as a “mirror” in the test tube.

is used to distinguish between an aldehyde and ketone. Tollens’ Test Tollens’ Test is used to distinguish between an aldehyde and ketone. does not oxidize alcohols or ethers.

Learning Check Write the condensed structural formula the following is mixed with Tollens’ reagent. Butanal

Butanal will oxidize to butanoic acid.. Answer… Butanal will oxidize to butanoic acid..

Learning Check Write the condensed structural formula when the following is mixed with Tollens’ reagent. Acetaldehyde

Solution Acetaldehyde will oxidize to acetic acid (ethanoic acid) Ethanoic acid, acetic acid

Learning Check Write the condensed structural formula when the following is mixed with Tollens’ reagent C. Ethyl methyl ketone

Solution Remember that there is no hydrogen to pull off of the carbon atom, so ketones do not oxidize (just like tertiary alcohols).

Cu2+ reacts with aldehydes that have an adjacent –OH group. Benedict’s Test In the Benedict’s test, Cu2+ reacts with aldehydes that have an adjacent –OH group. aldehydes are oxidized to carboxylic acids. Cu2+ is reduced to give Cu2O(s).

Benedict’s Test Because many sugars, such as glucose, contain this type of aldehyde grouping, Benedict’s reagent can be used to determine the presence of glucose in blood or urine.

Reduction of Aldehydes & Ketones Aldehydes and ketones are reduced by hydrogen (H2) with a catalyst or sodium borohydride (NaBH4), thus decreasing the number of carbon-oxygen bonds, reducing aldehydes to primary alcohols, and reducing ketones to secondary alcohols.

Reduction of Aldehydes and Ketones Aldehydes gives primary alcohols Ketones gives secondary alcohols

How reductions work…. The hydrogen from NaBH4 adds to the carbonyl carbon. The resulting ion protonates from the water.

Complimentary to oxidations… Tertiary alcohols cannot be formed (because there is no carbonyl that can be reduced to make them).

Try to give the product…

Something like this…

Try to give the product…

Something like this…

What would you need to start with to get this alcohol?

One way to draw the starting material…

Additional Practice for you after class…

Classify each as an aldehyde or ketone. Learning Check Classify each as an aldehyde or ketone. A. C. B. D.

Classify each as an aldehyde or ketone. Solution Classify each as an aldehyde or ketone. A. C. B. D. Ketone Aldehyde Aldehyde Ketone

Classify each as an aldehyde, ketone, alcohol, or ether. Learning Check Classify each as an aldehyde, ketone, alcohol, or ether. B. CH3─O─CH3 A. D. C.

A. B. CH3─O─CH3 Ketone Ether C. D. Alcohol Aldehyde Solution Classify each as an aldehyde, ketone, alcohol, or ether. A. B. CH3─O─CH3 Ketone Ether C. D. Alcohol Aldehyde

Give the IUPAC name for each structure below…

Solution A. B. 2-Pentanone; methyl propyl ketone C. Cyclohexanone 3,3-Dimethylbutanal

Name each of the following. Learning Check Name each of the following. A. B. C.

Name each of the following. Solution Name each of the following. A. Pentanal B. 3-Chloropropanal C. 2-Butanone