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Organic Chemisty > Ch 21 Carboxylic Acids and their Derivatives > Flashcards

Ch 21 Carboxylic Acids and their Derivatives Flashcards

1
Q

How do you name a carboxylic acid?

A

monocarboxylic acids,compounds containing one carboxylic acid group, are named with the suffix “-oic acid”

the parent chain includes the carbon atom of the carboxylic acid, that carbon is always assigned number 1 when naming the parent

when a carboxylic group is connected to a ring, the compound is named as an alkane carboxylic acid.

diacids,compounds containg two carboxylic acids groups ,are named with the suffix “dioic acid

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2
Q

oxalic acid

A
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3
Q

malonic acid

A
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4
Q

succinic acid

A
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5
Q

Glutaric acid

A
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6
Q

What is the hybridization, geometry and bond angle of carbon atom of a carboxylic acid?

A

sp2

Trigonal planar

120º

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7
Q

Why do carboxylic acids have higher boiling points than other compounds with OH groups?

A

carboxylic acid can form two hydrogen bonding interactions, allowing molecules to associate with each other in pairs. Stronger intermolecular forces.

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8
Q

Treatment of a carboxylic acid with strong base yields _____

A

Treatment of a carboxylic acid with a strong base yields a carboxylic salt

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9
Q

Carboxylate salts are ____ and are therefore more water soluble than their corresponding carboxylic acids.

A

Carboxylic salt are ionic and are therefor more water soluble than their their corresponding carboxylic acids

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10
Q

The pKa of most carboxylic acids is between __ and __.

A

The pKa of most carboxylic acids is between 4 and 5

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11
Q

Physiological pH

A

our blood is buffered to a pH of approximately 7.3

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12
Q

Explain the effects of electron withdrawing substituents on the acidity of a carboxylic acid.

A

Electron with drawing groups increase the acidity (decrease he pKa) of carboxylic acids.

The inductive effects can stabilize the conjugate base.

The effect of the EWG depends on its proximity to the carboxlic acid group.

the effect is most pronounced when the EWG is located at the alpha position. as the distance increase the effect becomes less pronounced

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13
Q

What happens when a carbon carbon triple bond(alkynes) is treated with 1).O3 the 2). H2O

A

Oxidative cleavage will break a triple bond froming two carboxylic acids

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14
Q

What happens when a primary alcohol is treated with Na2Cr2O7/H2SO4,H2O.

A

oxidation will occur and a carboxylic acid will be formed( a variety of strong oxidazing agens can be used to oxidize primary alcohols and produce carboxylic acids)

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15
Q

What happens when a alkyl benzen is treated with Na2Cr2O7/H2SO4,H2O

A

an alkyl group on an aromatic ring will be completely oxidized to give benzylic acid, provided that the benzylic postion has at least one hydrogen atom

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16
Q

When treated with aqueous acid and a nitrile ( a compound with a cyano group) can be converted into a ________

A

Carboxylic acid , this process is called hydrolysis

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17
Q

Give a two step process for convering an alky halide to a carboxylic acid. Via hydrolysis

A

The first step is an SN2 reaction in which a cyanide acts as a nucleophile. The resulting nitrile is then hydrolized to yield a carboxylic acid hat has one more carbon atom than the original alkyl halide.

the reaction cannot occur with tertiary alkyl halides

the 1).nitrile replace the halide and then hydroized with 2).H3O+/heat

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18
Q

Carboxylic acids can be prepared by treating a Grignard reagent with ______ and ____

A

Carboxylic acids can be prepared by treating a Grignard reagent with carbon dioxide and a proton source.

In the first step, the grinard reagent attacks the eletrophilic center of carbon dioxide, generating a carboxylate ion. Treating the carboxylate ion with a proton source affords a carboxylic acid.

The two step must occur separately becaue the proton source is not caompatible with the Grignard reagent

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19
Q

Give a two step process for converting an alkyl ( or vinyl or aryl) halide to a carboxylic acid

A
  1. Grinard reaction
  2. treatment with CO2

Adds a carbon atom

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20
Q

Carboxylic acids are reduced to alcohols upon treatment with _____

A

Carboxylic acids are reduced to alchols upon the tretmant of LAH and a H3O+ (proton source)

Or BH3 •THF, reduction with borane is often preferred over the reduction with LAH, beacuse borane reacts selectively with carboxylic acids in the presence of another carbonyl group

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21
Q

What are some common carboxylic acid derivatives?

A

acid halide

acid anhydride

ester

amide

any compound with a carbon atom that has three bonds to heteroatoms will be classified as a carboxylic acid derivative. (i.e nitrile)

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22
Q

how are acid are acid halides named?

A

acid halides are named as derivatives of carboxylic acids by replacinf the “ic acid” with “yl halide”

benzoic acid—> benzoyl chloride

when an acid halide group is connected to a ring, the suffix “carcoxylic acid” is replaced with “carbonyl halide”

cyclohexanecarboxylic acid ——>cyclohexanecarbonyl chloride

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23
Q

how are acid anhydrides named?

A

acid anhydrides are named as derivatives of carboxylic acids by replacing the suffix “acid “ with anhydride.

Succinic acid—-> succinic anhydride

Unsymmetrical anhydrides are prepared from two different carboxylic acids and are named by indicating
both acids alphabetically followed by the suffix “anhydride

Acetic benzoic anhydride

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24
Q

List the carboxylic acids in order of decreasing reactivity

A

OH>Cl>OOR>OR>NH2

cloride

anhydride

ester

nitrile

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25
Q

Explan the difference in reaivtiy of an acid cloride and a nitrile?

A

The third resonance(three lone pair on oxygen and a double bond on Cl) structure does not contribute much character to the overall resonance hybrid because the p-orbital overlap required for a C=Cl bond is not effective. As a result, the chlorine atom does not donate much electron density to the carbonyl group via resonance. The net effect of the chlorine atom is to withdraw electron density, rendering the carbonyl group extremely electrophilic.

Nitrogen is less electronegative than chlorine or oxygen and is not an effective electron-withdrawing group. The nitrogen atom does not withdraw much electron density from the carbonyl group, and inductive effects are not significant. However, resonance effects are substantial. Unlike an acid halide, the third resonance structure of an amide contributes significant character to the
overall resonance hybrid. The p orbital on the carbon atom effectively overlaps with a p orbital on the
nitrogen atom, and the nitrogen atom can easily accommodate the positive charge.

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26
Q

What is the major difference between carboxylic acid derivatives and aldehydels/ketones

A

carboxylic acid derivatives possess a heteroatom that can function as a leaving group, while aldehydes and ketones do not. When a nucleophile attacks a carboxylic acid derivative, a reaction can occur in which the nucleophile replaces the leaving group.

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27
Q

What are the two core step of a nucleophilic acyl substitution

A
  1. The carbonyl group is attacked by a nucleophile,forming a tetrahedral intermediate
  2. A leaving group is expelled, and the carbonyl group is re-formed

In the first step, a nucleophile attacks the carbonyl group, during which the hybridization state of the carbon atom changes. In both the starting material and product, the carbon atom is sp2 hybridized with trigonal planar geometry, but the same atom in the intermediate is sp3 hybridized with tetrahedral geometry. In recognition of this geometric change, the intermediate is often called a tetrahedral intermediate. In the second step, the carbonyl group is re-formed via loss of a leaving group. Re-formation of the CRO double bond is a powerful driving force, and even poor leaving groups (such as RO-) can be expelled under certain conditions.

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28
Q

Why do proton trasfers occur?

A

In acidic conditions, avoid formation of a strong base. In basic conditions, such as hydroxide or methoxide, avoid formation of a strong acid. This rule dictates that all participants in a reaction (reactants, intermediates, and leaving groups) should be consistent with the conditions employed.

The tetrahedral intermediate exhibits an oxygen atom with a localized negative charge, which is strongly basic and therefore inconsistentwith acidic conditions. To avoid formation of this intermediate, the acid catalyst is first employed to protonate
the carbonyl group (just as we saw in the previous chapter with ketones and aldehydes).

A protonated carbonyl group is significantly more electrophilic, and now when water attacks, no negative charge is formed. This step is now consistent with acidic conditions

Formation of a strong base must only be avoided in acidic conditions. The story is different under basic conditions. protonationof the carbonyl group would involve formation of a strong acid, which is not consistent with basic conditions. Under basic conditions, hydroxide attacks the carbonyl group directly to give a tetrahedral intermediate.

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29
Q

When do proton transfers occur?

A

A proton transfer can occur (1) before the nucleophilic attack, (2) before loss of the leaving group, or (3) at the end of the mechanism. Some mechanisms will have proton transfers at all three points,while other mechanisms might only exhibit one proton transfer step at the end of the mechanism

30
Q

reactions performed under acid-catalyzed conditions commonly have proton transfer steps at ______ possible points

A

reactions performed under acid-catalyzed conditions commonly have proton transfer steps at all three possible points

31
Q

Acid chlorides can be formed by treating carboxylic acids with ______

A

SOCl2

32
Q

Mech for the prepartion of acid chlorides via thionyl chloride.

A

The first part of the mechanism converts the OH group into a better leaving group, which is accomplished in three steps. Each of these three steps should seem familiar if we focus on the chemistry
of the S=O bond. In the three steps, the S=O bond behaves very much like a C=O bond of a carboxylic acid derivative (as described in the previous section). First, the S=O bond is attacked by a nucleophile, then it is re-formed to expel a leaving group, and finally a proton transfer is used to remove the charge. Part 2 of the mechanism is a typical nucleophilic acyl substitution, which is
accomplished in two steps: nucleophilic attack followed by loss of a leaving group. In this case, the leaving group further degrades to form gaseous SO2. Formation of a gas (which leaves the reaction
mixture) forces the reaction to completion.

33
Q

When treated with ___ acid chlorides are hydrolyzed to give carboxylic acids

A

water

34
Q

Mech for the hydrolysis of an acide chloride

A
35
Q

When treated with alchols (and pyridine),acid chlorides can be converted into ____

A

esters

pyrindine is used as a base to neutralize the HCl that is produced

36
Q

Why is pyridine used?

A

Pyridine is a base that reacts with HCl to form pyridinium chloride. This process effectively traps the HCl so that it is unavailable for any other side reactions.

37
Q

When treated with _____, acid chlorides are converted into amides

A

ammonia

pyridine is not used in this reaction because ammona itself is a sufficiently strong base to neutralize the HCl produced

For this reaction, two equivalents of ammonia are necessary: one for the nucleophilic attack and the other to neutralize the HCl. This reaction also occurs with primary and secondary amines to produce N-substituted amides

38
Q

When treated with Excess LAH and water , acid chlorides are reduced to give _____

A

alcohols

1) . Excess LAH
2) . H2O

39
Q

When treated with LiAl(OR)3H and water , acid chlorides are reduced to give _____

A

aldehydes

40
Q

When treated with Excess Grignard and water , acid chlorides are reduced to give _____

A

teretary alcohols

41
Q

When treated with a Gilman reagent (R2CuLi) , acid chlorides are reduced to give _____

A

Ketone

42
Q

Carboxylic acids can be converted in to acid anhydrides with______

A

excessive heating

water is relased

this method is only practical for acetic acid, as most other acids do not survive the heat

43
Q

When acid chlorides are treated with a carboxylate ion____ are produced

A

acid anhydrides

NaCl is relased

this method can be used to prepare symmetrical or unsymmetrical anhydrides

44
Q

The reactions of anhydrides are directly analogous to the reactions
of acid chlorides. The only difference is in the identity of
the ______

A

leaving group

With an acid chloride, the leaving group is a chloride ion, and the by-product of the reaction is
therefore HCl. With an acid anhydride, the leaving group is a carboxylate ion, and the by-product
is therefore a carboxylic acid. As a result, it is not necessary to use pyridine in reactions with acid
anhydrides, because HCl is not produced.

45
Q

Acetic anhydride can be used to acetylate an alcohol or and _____

A

Amine

46
Q

When treated with a strong base followed by an alkyl halide, carboxylic acids are converted into

A

esters

via Sn2 rections

47
Q

What is the mech for the preparation of esters via Sn2 reactions

A

The carboxylic acid is first deprotonated to yield a carboxylate ion, which then functions as a nucleophile and attacks the alkyl halide in an SN2 process. The expected limitations of SN2 processes therefore apply. Specifically, tertiary alkyl halides cannot be used.

48
Q

Carboxylic acids are converted into ____ when treated with an alcohol in the presence of an acid
catalyst.

A

esters

this process is called a fisher esterification

49
Q

What is the mech for a fisher esterification

A
50
Q

How do you prepare an ester from an acid chloride.

A

by teating the acid chloride with and alcohol and pyridine

51
Q

What happen when esters are treated irh sodium hydroxide then an acid?

A

the ester is converted into a carboxylic acid

52
Q

What is the mech for the saponification of ester?

A
53
Q

Esters can be hydrolized under____ conditions

A

esters can be hydrlized under acidic conditions

54
Q

What is the mech for an acid catalyzed hydrolysis of esters?

A
55
Q

Esters react slowy with ___ to yield amides

A

esters react slowly with amines to yield amides

56
Q

When treated with excess LAH ,esters are reduced to ______

A

When treated with excess LAH esters are reduced to yield alcohols.

57
Q

What is the mech for the reduction of an ester with LAH

A
58
Q

An ester can be treated with 1).DIBAH/2).H2O to produce ______.

A

Aldehydes

59
Q

What happens when an ester is treated with a Grignard reagent

A

When treated with a Grignard reagent, esters are reduced to yield alcohols with the introduction oftwo alkyl groups

60
Q

What is the mech for the reaction between an ester and a grignard reagent

A
61
Q

Amides can be prepared from _______ of the carboxylic acid derivatives. Which are the most efficient?

A

Amides can be prepared from any of the carboxylic acid derivatives discussed earlier in this chapter.

Among these methods, amides are most efficiently prepared from acid chlorides.

Acid halides are the most reactive of the carboxylic acid derivatives, so the yields are best when an acid chloride is used as a starting material.

62
Q

Amides are hydrolyzed to give _______ in the presence of aqueous acid aor base

A

amides can he hydrolyzed to give carboxylic acids in the presence of aqueous acid , but the process is slow and requires heating to occur at an appreaciable rate

Amides are also hydrolyzed when heated in basic aqueous solutions, although the process is very slow. The mechanism for this process is directly analogous to the saponification of
esters.

63
Q

What is the mech for the acid catalyzed hydrolysis of an amide?

A

The mechanism for this transformation (Mechanism 21.11) is directly analogous to the acid- catalyzed hydrolysis of esters (Section 21.11).
In this reaction, notice that an ammonium ion (NH4+) is formed as a by-product. Since the ammonium ion (pKa = 9.2) is a much weaker acid than H3O+ (pKa = -1.7), the equilibrium greatly favors formation of products, rendering the process effectively irreversible

64
Q

What is the mech for a hydrolysis of amides under basic canditions?

A
65
Q

What happens when an alkyl halide is treated with a cyanide ion

A

Nitriles are produced , along with the salt of the halide

this process proceeds via an Sn2 mech, so tertiary alkyl halides connot be used

66
Q

What happens when a amide is treated with SOCl2

A

a nitrile is formed in this dehydration

this process is useful fro preapring nitriles, which cannot be prepared via an Sn2 process

67
Q

In aqueous acidic conditions, nitriles are hydrolyzed to afford _____, which are then further hydrolyzed
to yield carboxylic acids.

A

In aqueous acidic conditions, nitriles are hydrolyzed to afford amides,which are then further hydrolyzed to yield carboxylic acids.

68
Q

What happens when an nitriles are treated with 1)NaOH,H2O/2)H3O+

A

Carboxylic acids are produced

69
Q

What is the mech for an acid catalyzed hydrolysis of nitrile

A
70
Q

what is the mech for the base catalyzed hydrolysis of nitriles

A
71
Q

What happens when a nitrile is treated with a Grignad reagent,followed by aqueous acid

A

a ketome is formed

the grignard reagent attacks the nitrile, much like it attaacks a carbonyl group

the resulting anion is then treated with aquesous acid to give an imine, which is then hydrolyzed to a ketone under acidic conditons.

72
Q

Nitriles are conveted to ____ when treated with LAH(excess) then a proton source.

A

nitriles are converted to amines when treated with LAH

Organic Chemisty (20 decks)

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