Carboxylic acids and Esters Flashcards
What are carboxylic acids?
Organic compounds containing both a carbonyl (C=O) and a hydroxy group (-OH) attached to the same carbon, known as the carboxyl group.
How can the carboxylic acid functional group be represented?
It can be represented in the following ways:
* RCOOH
* R
* 0-H
* Skeletal Formula
* Displayed Formula
* Structural Formula
What does ‘R’ represent in the carboxylic acid formulas?
The rest of the chain, which could be an alkyl group including a mixture of branches and/or other functional groups.
How do you name a carboxylic acid?
Start with the alkane, remove the ‘e’ and replace it with ‘oic acid’.
What is the numbering convention for carbon atoms in carboxylic acids?
The carbon atom that is part of the carboxylic acid functional group is always carbon 1.
What is the name of the compound with the formula CH3COOH?
Propanoic acid
How is 3-chlorobutanoic acid structured?
It has a chlorine atom on the third carbon of a butanoic acid structure.
What is the name of the compound with the structure CH3(CH2)4COOH?
Octanoic acid
Fill in the blank: To name a carboxylic acid, you replace the ‘e’ in the alkane name with ______.
oic acid
True or False: The carbon atom in the carboxylic acid functional group is always counted as carbon 2.
False
What is the significance of the carboxyl group in carboxylic acids?
It defines the functional properties of the acid, influencing its reactivity and solubility.
What type of acid are carboxylic acids classified as?
Weak acids
Carboxylic acids only partially dissociate in water.
What is the product of the reaction between ethanoic acid and sodium hydroxide?
Sodium ethanoate and water
Reaction: CH3COOH(aq) + NaOH(aq) → CH3COONa(aq) + H2O
What gas is produced when ethanoic acid reacts with sodium carbonate?
Carbon dioxide
Reaction: 2 CH3COOH(aq) + Na2CO3(aq) → 2 CH3COONa(aq) + H2O + CO2(g)
What is the result of the reaction between ethanoic acid and sodium metal?
Sodium ethanoate and hydrogen gas
Reaction: CH3COOH(aq) + Na(s) → CH3COONa(aq) + ½H2(g)
What is the name of the ion formed when carboxylic acids react under alkaline conditions?
Carboxylate ion
What is the relationship between carboxylic acids and carboxylate salts?
Carboxylate salts are formed when metal ions are present with carboxylate ions.
Carboxylate salts are ionic compounds.
Fill in the blank: The carboxylate ion is named after the carboxylic acid that forms it by replacing ‘-oic acid’ with ‘-______’.
oate
What are the physical properties of carboxylate salts?
- Soluble in water
- Good electrical conductivity in aqueous solution
- Relatively high melting point compared to the carboxylic acid
These properties are due to their ionic nature.
What do carboxylic acids react with alcohols to form?
esters
What are the two main functional groups present in esters?
Carbonyl (C=O) and alkyl (O-R) groups
Esters are characterized by the presence of these two functional groups.
How can esters be formed?
From the reaction between:
* Carboxylic acid and alcohol
* Acid anhydride and alcohol
* Acyl chloride and alcohol
These reactions are typical methods for synthesizing esters.
What is the naming convention for esters?
Named ‘back to front’, starting with the alkyl part and ending with the acid
This naming convention reflects the components that form the ester.
What is the ester formed from propanoic acid and ethanol?
Ethyl propanoate
The name is derived from the alcohol (ethyl) and the acid (propanoate).
Fill in the blank: The carbonyl group in esters is represented as _______.
C=O
The carbonyl group is a key feature of esters.
Fill in the blank: Esters can be formed from an acid anhydride and an _______.
Alcohol
This is one of the methods for ester formation.
True or False: The alkyl part of an ester is derived from the carboxylic acid.
False
The alkyl part comes from the alcohol, while the acid part comes from the carboxylic acid.
What is formed when an alcohol and carboxylic acid are warmed in the presence of concentrated sulphuric acid?
An ester is formed
The reaction is known as esterification.
What type of reaction occurs between an alcohol and a carboxylic acid to form an ester?
The reaction is both slow and reversible
This means that the ester can break down back into the reactants under certain conditions.
Fill in the blank: When ethanoic acid reacts with methanol in the presence of concentrated sulphuric acid, an _______ is produced.
ester
What is the role of concentrated sulphuric acid in the esterification process?
It acts as a catalyst
Catalysts speed up the reaction without being consumed.
True or False: The esterification reaction is irreversible.
False
The reaction is reversible, meaning the products can revert to reactants.
What are the two main reactants involved in the esterification process?
Alcohol and carboxylic acid
What are acid anhydrides?
Derivatives of carboxylic acids where the H of the hydroxy group has been replaced with a carbonyl group
Acid anhydrides are used in the formation of esters through reactions with alcohols.
What products are formed when an acid anhydride reacts with an alcohol?
An ester and a carboxylic acid
This reaction is a common method for synthesizing esters.
Do phenols readily react with carboxylic acids to form esters?
No
Phenols do not react readily with carboxylic acids, but they do react with acid anhydrides and acyl chlorides.
Which reagents can phenols react with to form esters?
Acid anhydrides and acyl chlorides
These reagents are effective due to the reactivity of the carbonyl group.
Why do phenols not react readily with carboxylic acids?
Due to the comparative non-availability of the lone electron pair on the O atom of the OH group
This non-availability affects the reactivity of phenols in ester formation.
What effect does the increased electron density on the phenol ring have?
Makes phenol more susceptible to electrophilic attack
This increased susceptibility is crucial for the reactivity of phenols with certain reagents.
What are the products of ester hydrolysis?
Carboxylic acid and alcohol
Esters can be hydrolyzed using water.
What is the catalyst used in acid hydrolysis of esters?
Hot aqueous acid
The acid acts as a catalyst in the reaction.
Is the reaction of acid hydrolysis of esters reversible?
Yes
The reaction can be reversed under certain conditions.
What type of hydrolysis uses hot aqueous alkali?
Base hydrolysis
This method is different from acid hydrolysis.
Is base hydrolysis of esters reversible?
No
This reaction is not reversible.
What is produced instead of carboxylic acid during base hydrolysis?
Carboxylate salt
This occurs in alkali conditions.
What is the process of hydrolyzing large esters found in fats and oils called?
Saponification
The sodium salt produced is similar to those found in soap.
Fill in the blank: Concentrated acid is used to make an ester, while _______ is used to hydrolyze it.
Dilute acid
This distinction is important for the hydrolysis process.
What are acyl chlorides?
Derivatives of carboxylic acids where the hydroxyl group is replaced by a chlorine atom
Acyl chlorides are characterized by their polar carbonyl bonds.
How do acyl chlorides react with other molecules?
They react readily due to very polar carbonyl bonds and form permanent dipole interactions
This reactivity is a key feature of acyl chlorides.
Give an example of an acyl chloride.
Ethanoyl chloride
Ethanoyl chloride is a common example used in organic synthesis.
How can acyl chlorides be prepared?
From carboxylic acids using thionyl chloride (SOCk)
Thionyl chloride is also known as sulfur dichloride oxide.
Fill in the blank: Acyl chlorides are derivatives of carboxylic acids where the hydroxyl group has been replaced by a _______.
Chlorine atom
True or False: Acyl chlorides do not have polar carbonyl bonds.
False
How does ammonia react with acyl chlorides to form primary amides?
ammonia is basic so will react with the HCl formed to make a salt.
-We use two ammonia molecules in the equation -
-the first reacts with the acyl chloride to produce the amide and HCl.
-The second NH3 mops up the HCl produced forming the salt NH4Cl
What are the reagents and conditions for the reaction with ammonia and acyl chloride?
Acyl chloride and excess ammonia
How do amines react with acyl chlorides to form secondary amides?
react with acyl chlorides in a similar way to ammonia, again products
salt from the reaction of the amine starting material with HCl produced in the reaction.
What does acylation refer to?
producing a molecule which contains an acyl group
What can act as acylation agents?
-Esters
-Amides
-Carboxylic acids
When is it not possible to use aldehydes or ketones as acylating agents?
under normal conditions
What is the general formula for esters?
O
II
R–C–OR
