Organic Chemistry- Carboxylic Acids Flashcards
Carboxylic acids with _____ and _____ are some of the most reactive organic molecules on test day.
Carbonyl and hydroxyl groups
Carboxylic acids are found in what?
In soups, oils, preservatives, skin care products, clothing, and amino acids
Carboxylic acids often have strong what?
Unpleasant odors
What are examples of carboxylic acids with strong odors?
Acetic acid (Vinegar) Propionic acids (swiss cheese) Butyric acid (rancid butter and body odor)
What makes carboxylic acid so interesting and versitile?
They’re acids, so they give away protons– particularly because when they do so, the reamining negative charge resonates between two oxygen atoms, making the anion very stable. Most acidic compounds encoutered in organic chemistry, with pKa between 3 and 6. Carboxylic acids are also excellent at hydrogen bonding, which results in large intermolecular forces and high boiling points.
Finally, carboylic acids are ubiquitous in nature and synthesized by all living organisims.
What does a carboxylic acid contain?
Both a carbonyl and a hydroxyl group, bonded to the same carbon
Why are carboxylic acids one of the most oxidized groups?
It has three bonds to oxygen atoms, making it one of the most oxidized functional groups encountered in organic chemistry
Carboxylic acids are always what?
Terminal groups
In the IUPAC system, how are carboxylic acids named?
By adding the suffix -oic acid to the parent root when the carboxylic acid is the highest-priority functional group. When this is true, the carbonyl carbon becomes carbon number 1
What is the common name of methanoic acid?
Formic acid
What is the common name of ethanoic acid?
Acetic acid
What is the common name of propanoic acid?
Propionic acid
How are cyclic carboxylic acid named?
By listing the cycloalkane with the suffix carboxylic acid
How are salts of carboxylic acids named?
Beginning with the cation, followed by the name of the acid with the ending -oate repalcing -oic acid.
Which carboxylic acids are common in biological systems?
Dicarboxylic acids
What do dycarboxylic acids contain?
Carboxylic acid group on each end of the molecule
What is the smallest dicarboxylic acid?
Oxalic acid with two carbons
After oxalic acid, what are the next 5 straight-chain dicarboxylic acids?
Malonic, succinic, glutaric, adipic, and pimelic acids
In the IUPAC system, how are dicarboxylic acids named?
They have the suffix -dioic acid
What is the IUPAC name for oxalic acid?
Ethanedioic acid
What is the IUPAC name for malonic acid?
Propanedioic acid
What is the IUPAC name for Succinic acid?
Butanedioic acid
What is the IUPAC name for Glutaric acid?
Pentanedioic acid
What is the IUPAC name for adipic acid?
Hexanedioic acid
What is the IUPAC name of pimelic acid?
Heptanedioic acid
What is an example of cyclic carboxylic acid and carboxylic acid salt?
1-chloro-2-methlcyclo-pentane carboxylic acid (Cyclic) sodium hexanoate (Salt)
Many physical properties of carboxylic acid are similar to what? Why?
To aldehydes and ketones because they both contain carbonyl groups
What makes carboxylic acid different from aldehydes and ketones?
The additional hydroxyl group permits carboxylic acids to hydrogen bond and provides another acidic hydrogen that can participate in reactions.
Why are carboxylic acids polar?
Because they contain a carbonyl group
Why can carboxylic acids form hydrogen bonds?
Because they contain a hydrogen bonded to a very elecronegative atom
Why do carboxylic acids display strong intermolecular attractions?
Because both the hydroxyl oxygen and carbonyl oxygen can participate in hydrogen bonding.
Carboxylic acids tend to form what?
Dimers
What are Dimers?
Pairs of molecules connected by two hydrogen bonds.
Multiple hydrogen bonds do what?
Elevate the boiling and melting points of carboxylic acids past those of corresponding alcohols.
Boiling points also increase with what?
With increasing molecular weight
What is acidic in the carboxylic acid?
The hydroxyl hydrogen of a carboxylic acid
What happens when the hydrogen is removed from the carboxylic acid?
This results in a negative charge that remains after the hydrogen is removed and resonance stabilization occurs between both of the electronegative oxygen atoms.
Delocalization of th enegative charge results in what?
A very stable carboxylate anion
The more stable the conjugate base, the easier it is for _______? And thus, the _________.
For the proton to leave, and thus, the stronger the acid.
What is the pKa value for ethanoic acid?
4.8
What is the pKa for propanoic acid?
4.9
How does carboxylic acid compare to strong acids?
They do not compare to strong acids like HCL with a pKa of -8 or HSO4 with a pKa of 1.99
What influences Anion stability?
Substituents on carbon atoms near a carboxyl group
Anion stability influences what?
Affect acidity
Groups like -NO2 or halides are _______ and increase _______.
Electron-withdrawing and increase acidity
Groups like -NH2 or -OCH3 are what? That What? Decreasing What?
Electron-donating groups that destabilize the negative charge, decreasing the acidity of the compound
The effects of each group are affected by what?
The closer the substituent groups are to the ccarboxyl group the greater the effect
In dicarboxylic acid, each _____ group influences the _____group.
Each -COOH group influence the -COOH group
Carboxylic acids are what? Due to what?
Electron-withdrawing due to the electronegativ oxygen atom they contain
Dicarboxylic acids are more _____ than the analogous monocarboxylic acids.
Acidic
How is the carboxylate anion formed?
When one proton is removed from the molecule
When the carboxylate anion is formed, what is the results? Why?
Results in an immediate decrease in the acidity of the reamining carboxylic acid.
If the second group were deprotonated it would create a doubly charged species with two negative charges repelling each other. Due to this instability, the second proton is actually less acidic (harder to remove) than the analogous proton of a monocarboxylic acid
What is a beta-dicarboxylic acid?
Are dicarboxylic acids in which each carboxylic acid is positioned on the beta-carbon of the other.
There are two carboxylic acids separated by a single carbon
What is notable about beta-dicarboxylic acids?
These compounds for the high acidity of the alpha-hydrogen located on the carbon between the two carboxyl groups (pKa: 9-14)
What happens with the loss of the alpha-hydrogen of a beta-dicarboxylic acid?
Produces a carbanion, which is stabilized by the electron-withdrawing effect of both carboxyl groups
What other molecules share the same result with the loss of the alpha-hydrogen?
Beta-diketone
Beta-ketoacid
Beta-dialdehydes
How can carboxylic acids be produced?
Via oxidation of the aldehydes and primary alcohols
What is the common oxidants to produce carboxylic acids?
A dichromate salt (Na2Cr2O7 or K2Cr2O7)
Chromium trioxide (CrO3)
Potassium permanganate (KMnO4)
Several other oxidizing agents can work
Can secondary or tertiery alcohols be oxidized to carboxylic acids? Why?
No because they already have at least two bonds to other carbons
Many reactions involving carbodylic acids proceed via what mechanism?
A single mechanism: Nucleophilic acyl substitution
What is nucleophilic acyl substitution similar to?
Nucleophilic addition to an aldehyde or ketone
How is nucleophilic acyl substitution different then nucleophilic addition?
Focuses on the existence of a leaving group in carboxylic acids and their derivatives
During nucleophilic acyl substituion, after opening the carbonyl via nucleophilic attack what happens?
Tetrahedral intermediate is formed and then the carbonyl can reform, thereby kicking off the leaving group
In nucleophilic acyl substitution, the nucleophilic molecule replaces what?
The leaving group of an acyl derivative
What is an acyl derivative?
Encompass all molecules with a carboxylic acid-derived carbonyl, including carboxylic acids, amides, esters, anhydrides and others
Acyl derivative are favored by what?
Good leaving groups
Also either in acidic or basic conditions, which can alter the reactivity of the electrophile and nucleophile
What makes good leaving groups?
Weak bases, which are often the conjugate bases of strong acids
How can carboxylic acid be converted into amides?
If the in coming nucleophile is ammonia (NH3) or an amine
What type of solution should be used to form an amide from carboxylic acid through nucleophilic acyl substitution?
Either an acidic or basic solution
How are amides named?
By replacing the -oic acid suffix with -amide in the name of the parent carboxylic acid. Any alkyl groups on the nitrogen are placed at the beginnin gof the name with the prefix N-
Amides exist in what state?
A resonance state where delocalization of electrons occurs between the oxygen and nitrogen atoms.
Amides that are cyclic are called what?
Lactams
How are lactams named?
By replacing the -oic acid with -lactam. They may also be named by indicating the specific carbon that is bonded during cyclization of the compound.
What are esters?
Are hybrid between a carboxylic acid and an ether (ROR)
How can esters be made?
By reacting carboxylic acids with alcohols under acidic conditions
What is esterification?
Is a condensation reaction with water as a side product
What is involved in esterification?
In acidic solutions, the carbonyl oxygen can be protonated which enhances the polarity of the bond, thereby prlacing additional positive charge on the carbonyl carbon and increasing its susceptibility to nucleophilic attack. This condensation reaction occurs most rapidly with primary alcohols.
What are examples of lactams?
beta-lactam
delta-lactam
sigma-lactam
Esters are named in the same manner as what?
As salts of carboxylic acids. The common name of ethyl acetate, or the IUPAC name ethyle ethanoate
What are esters that are cyclic called?
Lactones
How are lactones named?
By replacing the -oic acid with -lactone
What are examples of lactones?
alpha-acetolactone
beta-propiolactone
delta-valerolactone
How are anhydrides formed?
By condensation of two carboxylic acids. Anhydride formation occurs via nucleophilic acyl substitution.
What is one examples of anhydride formation?
The condesnation of two molecules of ethanoic acid to form ethanoic anhydride
How can carboxylic acids be reduced?
To primary alcohols by the use of Lithium aluminum bydride (LiAlH4)
What may be formed in the course of carboxylic acid reduction? What will happen to them?
Aldehyde intermediates
They will be reduced to alcohol
How does reduction of carboxylic acid occur?
By nucleophilic addition of hydride to the carbonyl group.
Will weaker reducing agents like sodium borohydride reduce carboxylic acid to alcohol?
No it is not strong enough
What is decarboxylation?
The complete loss of the carboxyl group as carbon dioxide
Dearboxylation is a common way to get rid of what?
A carbon from the parent chain.
1,3-dicarboxylic acid and other beta-keto acids may spontaneously what?
Decarboxylate when heated.
During decarboyxlation the carboxyl group is what and replaced with what?
Lost and replaced with hydrogen
Why does the decarboxylation reaction proceed through a six-membered ring?
Because both the electrophile and nucleophil are in the same molecules
What is initially formed in a decarboxylation reaction? How?
The enol
What happnes to the enol that is initially formed in a decarboxylation reaction?
Tautomerizes to the more stable keto form
What is sponification?
When long-chain carboxylic acids react with sodium or potassium hydroxide, a salt is formed
How does sponification occur?
By mixing fatty acids with lye (sodium or potassium hydroxide)
What is the result of sponification?
The formation of a salt that we know as soup
Soups can ______ nonpolar organic compounds in aqueous solutions, why?
Solvate
Beccause they contain both a nopolar tail and a polar carboxylate head
How are micelles made?
When placed in aqueous solution, soap molecules arrange themselves into spherical structure called micelles
What do micelles look like?
The polar heads face outward, where they can be solvated by water, and the nonpolar hydrocarbon chains are oriented toward the inside of the sphere, protected from the solvent.
What happens to the nonpolar molecules when interacting with micelles?
Dissolved in the hydrocarbon interior of the shperical micelle
What eventually happens to the micelle in water?
It dissolved in water due to the polarity of its exterior surface.
What is the underlying concept, when dealing with carboxylic acids?
The more stable the conjugate base is, the more likely it is that the proton will leave.
What is the stability of a conjugate base dependent on?
By three factors:
Periodic trends (electronegativity, and thus induction0
Size of the anion
Resonance
The reactions of carboxylic acids are dictated by what?
By the polarity of the carbonyl group in conjunction with the ability of the hydroxyl group to act as a leaving group.
