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14 Cards in this Set
- Front
- Back
Characteristics of a carbonyl
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-Carbon double bonded to oxygen
-double bond is shorter and stronger than an alkene -planar stereochemistry -partial negative charge on oxygen, partial positive charge on carbon |
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Carbonyl: Nucleophilic addition or substitution?
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-Aldehydes and ketones typically undergo nucleophilic addition
-Other carbonyl compounds prefer nucleophilic substitution |
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Physical properties of aldehydes and ketones
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-More polar and have higher boiling points than alkanes and alkenes of similar molecular weight.
-cannot H-bond with each other, so have lower b.p. than corresponding alcohols -less acidic than alcohols. -any electron withdrawing groups attache to an alpha carbon or the carbonyl tend to stabalize the conjugate base- increase acidity. -exist at room temp. as enol tautomers. |
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Chemical properties of aldehydes and ketones
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Typically act in one of two ways:
1. substrate in nucleophilic addition 2. Bronsted-Lowry acid by donating an alpha-hydrogen. -form an enolate ion when the alpha-H is removed, stabilized by resonance. |
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alpha-carbon
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-A carbon that is attached to a carbonyl carbon
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Tautomerization
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A reaction at equilibrium that involves a proton shift.
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Carboxylic acids-reactions
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-Typically behave as an acid or as a substrate in a nucleophilic substitution reaction
-when the hydroxyl group is protonated, it makes a good leaving group and substitution results. |
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Acid strength of carboxylic acid
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-considered very strong organic acids- when the proton is removed the conjugate base is stabilized by resonance.
-electron withdrawing groups on the alpha carbon further stabilize the conjugate base, thus increasing the acidity of the corresponding carboxylic acid |
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M.P. and B.P of carboxylic acids
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-make strong hydrogen bonds to form a dimer, increases b.p. of carboxylic acids by effectively doubling the MW of the molecules leaving the liquid phase.
-double bonds in unsaturated carboxylic acids impede the crystal lattice and lower the MP. |
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Solubility of carboxylic acids
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-Carboxylic acids with 4C or less are miscible with water
-soluble in most nonpolar solvents because the dimer formed allows the carboxylic acid to solvate without disrupting the H-bonds of the dimer. |
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Physical properties of amines
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-ammonia and amines hydrogen bond, raising the boiling point and increasing solubility with water.
-higher b.p than alkanes, lower b.p. than alcohols |
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Chemical properties of amines
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-Nitrogen can take either 3 or 4 bonds
-act as weak bases by donating their pair of electrons -electron donating substituents (ex. methyl groups) increase the basicity of an amine. 3 important things to remember for MCAT: 1. may act as Lewis base donating pair of electrons 2. may act as a nucleophile where the lone pair of electrons attacks a positive charge 3. nitrogen can take on a fourth bond |
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Properties of amides
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-Can act as either weak bases or acids
-Less basic than amines due to electron withdrawing properties of the carbonyl -hydrolyzed by either strong acids or strong bases -amides with a hydrogen attached to a nitrogen are able to H-bond to each other. |
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lactams
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-cyclic amides are called lactams
-highly reactive due to ring strain (even though amides are typically the least reactive carboxylic acid derivatives). |