General Introduction of Carboxylic Acids and Their Derivatives Questions in English

(C) The compound $(RCO)_2NH$ is a derivative of ammonia where two hydrogen atoms are replaced by acyl groups $(RCO-)$.
This structure is known as a secondary amide or an imide.
Thus,$(RCO)_2NH$ is a secondary amide.

(A) The acidic nature of carboxylic acids is primarily due to the resonance stabilization of the carboxylate ion $(R-COO^-)$ formed after the loss of a proton $(H^+)$.
The resonance structures of the carboxylic acid group are:
$R-C(=O)OH \leftrightarrow R-C(O^-)=O^+H$
This resonance allows the negative charge to be delocalized over two oxygen atoms in the carboxylate ion,making the release of the proton favorable.
Option $(A)$ represents the structure of the carboxylic acid group itself,which undergoes this resonance stabilization.

(D) The general formula $(RCO)_2O$ represents an acid anhydride.
It is formed by the dehydration of two molecules of carboxylic acid:
$2RCOOH \xrightarrow{-H_2O} (RCO)_2O$ (Acid anhydride)

(A) The chemical formula of acetamide is $CH_3CONH_2$.
By observing the molecular formula,we can see that it contains only one oxygen atom.

(B) The general formula $C_nH_{2n}O_2$ represents compounds with a degree of unsaturation (double bond equivalent) of $1$.
For carboxylic acids $(R-COOH)$,the general formula is $C_nH_{2n}O_2$.
For example,acetic acid $(CH_3COOH)$ has $n=2$,giving $C_2H_4O_2$.
Diketones,diols,and dialdehydes generally have different general formulas or require different degrees of unsaturation.
Thus,the correct option is $B$.

(B) The given structure is $HCOCl$. It is the acid chloride of formic acid $(HCOOH)$,hence it is called formyl chloride.

(B) . Urea is the diamide of carbonic acid.
$\mathop {HO - \mathop {\mathop C\limits^{||} }\limits^O - OH}\limits_{\text{carbonic acid}} + 2NH_3$ $\xrightarrow{- 2H_2O} \mathop {H_2N - \mathop {\mathop C\limits^{||} }\limits^O - NH_2}\limits_{\text{Urea}}$
Since two moles of $NH_3$ are required to replace both hydroxyl groups of carbonic acid,it is classified as the diamide of carbonic acid.

(A) Formamide,also known as methanamide,is the simplest amide derived from formic acid. Its chemical formula is $HCONH_2$. The structure is shown below:
$H-CO-NH_2$

(B) The $IUPAC$ name for $CH_3COOH$ is ethanoic acid because it contains two carbon atoms in its structure.
$HCOOH$ is methanoic acid.
$CH_3CH_2COOH$ is propanoic acid.
$CH_3CH_2CH_2COOH$ is butanoic acid.

(D) Vinegar is a dilute solution of acetic acid $(CH_3COOH)$.
It is produced by the fermentation of ethyl alcohol in the presence of the enzyme $Acetobacter$.

(C) The structures of the given compounds are as follows:
$1$. Aspirin: $2$-acetoxybenzoic acid,which contains a $-COOH$ group.
$2$. Benzoic acid: $C_6H_5COOH$,which contains a $-COOH$ group.
$3$. Picric acid: $2,4,6$-trinitrophenol,which contains an $-OH$ group and three $-NO_2$ groups,but no $-COOH$ group.
$4$. Salicylic acid: $2$-hydroxybenzoic acid,which contains a $-COOH$ group.
Therefore,the correct option is $(c)$.

(C) Soap is chemically defined as the sodium or potassium salt of long-chain carboxylic acids,also known as higher fatty acids.
These are typically produced by the saponification of fats or oils with an alkali like $NaOH$ or $KOH$.

(B) The compound $CH_3CN$ is named acetonitrile because it contains a methyl group attached to a cyanide group,which upon complete hydrolysis yields acetic acid $(CH_3COOH)$.
Specifically,$CH_3CN + 2H_2O \xrightarrow{H^+} CH_3COOH + NH_3$.

(B) The compound ${C_6}{H_5}COCl$ consists of a benzene ring attached to a carbonyl chloride group.
According to $IUPAC$ nomenclature rules,when the $-COCl$ group is attached directly to a ring,the suffix used is 'carbonyl chloride'.
Therefore,the parent name is benzene and the suffix is carbonyl chloride,resulting in the name 'Benzene carbonyl chloride'.

(B) The general formula $C_nH_{2n}O_2$ corresponds to compounds with a degree of unsaturation (double bond equivalent) of $1$.
Carboxylic acids have the general formula $C_nH_{2n}O_2$ (e.g.,acetic acid $CH_3COOH$ is $C_2H_4O_2$,where $n=2$).
Esters also share this general formula.
Diketones,diols,and dialdehydes generally have different hydrogen counts for the same number of carbons or require different degrees of unsaturation.

(D) The given structure is $CH_3-CO-O-CHO$.
This is an acid anhydride formed from two different carboxylic acids: ethanoic acid $(CH_3COOH)$ and methanoic acid $(HCOOH)$.
According to $IUPAC$ nomenclature for acid anhydrides,the names of the parent acids are written in alphabetical order followed by the word 'anhydride'.
Thus,the name is ethanoic methanoic anhydride.

(B) The general formula $C_nH_{2n}O_2$ represents compounds that have two oxygen atoms and a degree of unsaturation of $1$.
Carboxylic acids $(R-COOH)$ and esters $(R-COOR')$ both follow the general formula $C_nH_{2n}O_2$.
For example,acetic acid $(CH_3COOH)$ has the formula $C_2H_4O_2$,which fits the $C_nH_{2n}O_2$ pattern where $n=2$.

(A) The structure $CH_3-CH=CH-COOH$ is a four-carbon unsaturated carboxylic acid.
Its $IUPAC$ name is $But-2-enoic \ acid$.
The common name for this specific compound is $Crotonic \ acid$.

(C) The general formula $(RCO)_2O$ can be written as $R-CO-O-CO-R$. This structure represents an acid anhydride,which is formed by the dehydration of two carboxylic acid molecules.

(C) An acyl group is a functional group with the general formula $R-C(=O)-$,which is derived by removing the hydroxyl group $(-OH)$ from a carboxylic acid $(R-COOH)$.

(C) The general formula for an ester is $R-COO-R'$.
For the first member,the smallest alkyl groups must be attached to the functional group.
The simplest carboxylic acid is formic acid $(HCOOH)$ and the simplest alcohol is methanol $(CH_3OH)$.
Combining these,we get $HCOOCH_3$,which is methyl methanoate.
Thus,methyl methanoate is the first member of the ester homologous series.

(C) Crotonic acid is a short-chain unsaturated carboxylic acid.
Its chemical formula is $CH_3-CH=CH-COOH$ and its $IUPAC$ name is $(E)-\text{but}-2-\text{enoic acid}$.

(D) Isopropyl methanoate is an ester formed from methanoic acid $(HCOOH)$ and isopropyl alcohol $((CH_3)_2CHOH)$.
In the esterification reaction,the acyl group from methanoic acid is $H-CO-$ and the alkoxy group from the isopropyl alcohol is $-O-CH(CH_3)_2$.
Combining these,the structural formula is $H-CO-O-CH(CH_3)_2$,which can also be written as $H-CO-O-CH(CH_3)-CH_3$.

(D) The given structure is a cyclic anhydride derived from succinic acid (butanedioic acid).
In $IUPAC$ nomenclature,cyclic anhydrides are named by replacing the word 'acid' with 'anhydride' in the name of the corresponding dicarboxylic acid.
The parent dicarboxylic acid is butanedioic acid.
Therefore,the cyclic anhydride is named butanedioic anhydride.

(B) Methyl salicylate,commonly known as oil of wintergreen,has the chemical structure of an ester formed from salicylic acid and methanol. Its $IUPAC$ name is methyl $2-$hydroxybenzoate. The structure consists of a benzene ring with a hydroxyl group $(-OH)$ at the ortho position relative to a methyl ester group $(-COOCH_3)$.

(C) The given structure is a cyclic anhydride derived from $2,3-$dimethylbutanedioic acid (also known as dimethylsuccinic acid).
In $IUPAC$ nomenclature,cyclic anhydrides are named by replacing the word 'acid' with 'anhydride' in the name of the corresponding dicarboxylic acid.
The parent dicarboxylic acid is $2,3-$dimethylbutanedioic acid.
Therefore,the cyclic anhydride is named $2,3-$dimethylbutanedioic anhydride.

(C) The general formula for dicarboxylic acids is $HOOC-(CH_2)_n-COOH$.
For $n = 0$,it is Oxalic acid $(HOOC-COOH)$.
For $n = 1$,it is Malonic acid $(HOOC-CH_2-COOH)$.
For $n = 2$,it is Succinic acid $(HOOC-(CH_2)_2-COOH)$.
For $n = 3$,it is Glutaric acid $(HOOC-(CH_2)_3-COOH)$.
For $n = 4$,it is Adipic acid $(HOOC-(CH_2)_4-COOH)$.
Therefore,for $n = 4$,the acid is Adipic acid.

(C) Butyric acid,also known as butanoic acid $(CH_3CH_2CH_2COOH)$,is found in milk and butter.
It is a product of anaerobic fermentation and is responsible for the characteristic unpleasant smell and acrid taste of rancid butter.

(C) Functional isomers are compounds that have the same molecular formula but different functional groups.
Monocarboxylic acids (general formula $C_nH_{2n}O_2$) are functional isomers of esters (general formula $C_nH_{2n}O_2$).
For example,$CH_3COOH$ (Acetic acid) and $HCOOCH_3$ (Methyl formate) both have the molecular formula $C_2H_4O_2$.

(N/A) $(i)$ $4-$methylpentanal
$(ii)$ $6-$chloro$-4-$ethylhexan$-3-$one
$(iii)$ but$-2-$enal
$(iv)$ pentane$-2,4-$dione
$(v)$ $3,3,5-$trimethylhexan$-2-$one
$(vi)$ $3,3-$dimethylbutanoic acid
$(vii)$ benzene$-1,4-$dicarbaldehyde

(N/A) Organic compounds containing a carbon-oxygen double bond $(C=O)$ are called carbonyl compounds. The carbon atom of the carbonyl group is $sp^2$ hybridized and forms three sigma bonds. The homologous series of carbonyl compounds are as follows:

Name of homologous series	Common formula	Functional group
$(i)$ Aldehydes	$R-CHO$	$-CHO$
$(ii)$ Ketones	$R-CO-R'$	$>C=O$
$(iii)$ Carboxylic acids	$R-COOH$	$-COOH$
$(iv)$ Esters	$R-COOR'$	$-COOR'$
$(v)$ Acid halides	$R-COX$	$-COX$
$(vi)$ Amides	$R-CONH_2$	$-CONH_2$

(N/A) Carboxylic acid and carboxyl group:
$(i)$ Compounds that contain a carboxyl group $(-COOH)$ as a functional group are known as carboxylic acids.
$(ii)$ In a carboxyl group,a carbonyl group $(C=O)$ is attached to a hydroxyl group $(-OH)$. The name 'carboxyl' is derived from 'carbonyl' and 'hydroxyl'.
$(iii)$ The carboxyl group contains both a carbonyl group and a hydroxyl group.
$(b)$ Aliphatic and aromatic carboxylic acids:
| Aliphatic carboxylic acid | Aromatic carboxylic acid |
| :--- | :--- |
| $R-COOH$ | $Ar-COOH$ |
| The carboxyl carbon is attached to an alkyl group. | The carboxyl carbon is attached to an aryl group. |
| e.g.,$CH_3COOH$ | e.g.,$C_6H_5COOH$ |
$(c)$ Fatty acids: Naturally occurring aliphatic carboxylic acids with long carbon chains (typically $C_{12}$ to $C_{18}$) are known as fatty acids. They are often found as esters of glycerol in natural fats and oils.

(N/A) Common names:
$(a)$ Carboxylic acid compounds were first obtained from nature,hence most of the acid compounds are known by their common names. In common nomenclature of acids,the suffix 'ic acid' is used,which is based on the natural source of the acid.
$(i)$ Formic acid is first obtained from red ant (formica).
$(ii)$ Acetic acid is obtained from vinegar.
$(iii)$ Butyric acid is obtained from rancid butter.
$(b)$ Often,substituted groups are indicated by $\alpha, \beta, \gamma \ldots$ starting from the carbon atom adjacent to the $-COOH$ group.
e.g.,$^{\beta} CH_{3} - ^{\alpha} CH(OH) - COOH$
$(B)$ $IUPAC$ nomenclature of aliphatic acids:
$(a)$ For naming aliphatic carboxylic acids,the suffix 'oic acid' is added by replacing the 'e' of the corresponding alkane.
$(i)$ $HCOOH$ is named methanoic acid.
$(ii)$ $CH_{3}COOH$ is named ethanoic acid.
$(b)$ In the carbon chain,the carbon atom of the carboxylic acid group is assigned the number $1$.
$(c)$ If more than one $-COOH$ group is present,the prefixes di-,tri-,etc.,are used before 'oic acid',and the 'e' of the alkane is not removed.
$(i)$ $HOOC-COOH$: Ethanedioic acid
$(ii)$ $HOOC-CH_{2}-CH_{2}-COOH$: Butanedioic acid
Examples of $IUPAC$ nomenclature:
| Structure | $IUPAC$ name |
| :--- | :--- |
| $(i) \ CH_{3}-CH(CH_{3})-CH_{2}-COOH$ | $3$-methylbutanoic acid |
| $(ii) \ CH_{3}-CH(Cl)-COOH$ | $2$-chloropropanoic acid |
| $(iii) \ CH_{3}-CH(OH)-COOH$ | $2$-hydroxypropanoic acid |
| $(iv) \ CH_{3}-CO-CH_{2}-CH_{2}-COOH$ | $4$-oxopentanoic acid |

(N/A) The nomenclature of carboxylic acids involves identifying the longest carbon chain containing the $-COOH$ group.
$(i) \ HCOOH$: Contains $1$ carbon atom. Common name: Formic acid; $IUPAC$ name: Methanoic acid.
$(ii) \ CH_3COOH$: Contains $2$ carbon atoms. Common name: Acetic acid; $IUPAC$ name: Ethanoic acid.
$(iii) \ CH_3CH_2COOH$: Contains $3$ carbon atoms. Common name: Propionic acid; $IUPAC$ name: Propanoic acid.
$(iv) \ C_6H_5COOH$: $A$ benzene ring attached to a $-COOH$ group. Common name: Benzoic acid; $IUPAC$ name: Benzenecarboxylic acid (also accepted as Benzoic acid).
$(v) \ (COOH)_2$: Contains $2$ carbon atoms. Common name: Oxalic acid; $IUPAC$ name: Ethanedioic acid.
$(vi) \ HOOCCH_2CH_2COOH$: Contains $4$ carbon atoms. Common name: Succinic acid; $IUPAC$ name: Butanedioic acid.

(A) The table provides the common names,structural formulas,and $IUPAC$ names for various carboxylic acids:
| Common Name | Structural Formula | $IUPAC$ Name |
| :--- | :--- | :--- |
| $(i)$ Butyric acid | $CH_3CH_2CH_2COOH$ | Butanoic acid |
| $(ii)$ Isobutyric acid | $(CH_3)_2CHCOOH$ | $2$-methylpropanoic acid |
| $(iii)$ Malonic acid | $HOOC-CH_2-COOH$ | Propanedioic acid |
| $(iv)$ Glutaric acid | $HOOC-(CH_2)_3-COOH$ | Pentanedioic acid |
| $(v)$ Phenyl acetic acid | $C_6H_5CH_2COOH$ | $2$-phenylethanoic acid |
| $(vi)$ Malic acid | $HOOC-CH(OH)-CH_2-COOH$ | $2$-hydroxybutanedioic acid |

The carbon atom in the carboxyl group is $sp^{2}$ hybridized.
This results in a planar structure where the three bonds around the carbonyl carbon are at an angle of approximately $120^{\circ}$ to each other.
The carboxylic carbon is less electrophilic than the carbonyl carbon in aldehydes and ketones because of the resonance effect,where the lone pair of electrons on the hydroxyl oxygen atom is delocalized over the carbonyl group,reducing the partial positive charge on the carbon atom.

(N/A) $1-$bromoheptane: The parent chain is heptane ($7$ carbons). $A$ bromine atom is attached to the $1^{st}$ carbon.
$CH_2Br-CH_2-CH_2-CH_2-CH_2-CH_2-CH_3$
$(b)$ $5-$bromoheptanoic acid: The parent chain is heptanoic acid ($7$ carbons,including the carboxylic acid carbon). $A$ bromine atom is attached to the $5^{th}$ carbon.
$CH_3-CH_2-CH(Br)-CH_2-CH_2-CH_2-COOH$

(A) Let us analyze the structures of the given compounds:
$1$. Sulphanilic acid $(p-NH_2C_6H_4SO_3H)$: Contains a sulphonic acid group $(-SO_3H)$,not a carboxylic acid group $(-COOH)$.
$2$. Picric acid ($2,4,6-$trinitrophenol): Contains a phenolic hydroxyl group $(-OH)$ and nitro groups $(-NO_2)$,not a carboxylic acid group $(-COOH)$.
$3$. Aspirin (Acetylsalicylic acid): Contains a carboxylic acid group $(-COOH)$ and an ester group.
$4$. Ascorbic acid (Vitamin $C$): Contains hydroxyl groups and a cyclic ester (lactone),not a carboxylic acid group $(-COOH)$.
Thus,only Aspirin contains the $-COOH$ group.
The total number of such compounds is $1$.

(B) The molecule with the formula $C_{12}O_9$ is known as mellitic anhydride.
Its structure consists of a benzene ring fused with three cyclic anhydride groups.
Therefore,the functional group present in the molecule is an anhydride group.

(A) An anhydride is a functional group characterized by two acyl groups $(R-CO-)$ bonded to the same oxygen atom,represented by the general formula $R-CO-O-CO-R$.
In option $(A)$,the structure is $CH_3-CO-O-CO-CH_3$,which is acetic anhydride.
Option $(B)$ is an ether,while options $(C)$ and $(D)$ are esters.

(B) The general formula for mono carboxylic acids is $C_nH_{2n}O_2$ (where $n \geq 1$).
The first member $(n=1)$ is methanoic acid $(HCOOH)$,which is $CH_2O_2$.
The second member $(n=2)$ is ethanoic acid $(CH_3COOH)$,which has the molecular formula $C_2H_4O_2$.
Therefore,the second homologue is $C_2H_4O_2$.

(D) The carboxyl functional group is represented as $-COOH$.
$1$. Picric acid ($2,4,6$-trinitrophenol) contains a phenolic $-OH$ group and three nitro groups $(-NO_2)$,but no $-COOH$ group.
$2$. Barbituric acid contains amide groups within a heterocyclic ring,but no $-COOH$ group.
$3$. Ascorbic acid (Vitamin $C$) contains hydroxyl groups and a lactone ring,but no $-COOH$ group.
$4$. Aspirin (acetylsalicylic acid) is $2$-acetoxybenzoic acid,which contains a benzene ring substituted with an acetoxy group $(-OCOCH_3)$ and a carboxylic acid group $(-COOH)$.
Therefore,the correct option is $D$.

(C) The common names of lower fatty acids are derived from the natural sources from which they were first isolated.
For example,formic acid $(HCOOH)$ is named after the red ant (Latin: $formica$),from which it was first obtained.

(C) dicarboxylic acid contains two carboxylic acid groups $(-COOH)$.
$1$. Adipic acid is $HOOC-(CH_2)_4-COOH$ (hexanedioic acid).
$2$. Glutaric acid is $HOOC-(CH_2)_3-COOH$ (pentanedioic acid).
$3$. Malonic acid is $HOOC-CH_2-COOH$ (propanedioic acid).
$4$. Valeric acid is $CH_3-(CH_2)_3-COOH$ (pentanoic acid),which is a monocarboxylic acid.
Therefore,Valeric acid is not a dicarboxylic acid.

(A) dicarboxylic acid contains two carboxyl $(-COOH)$ groups in its structure.
$1$. Citric acid has the structure $HOOC-CH_2-C(OH)(COOH)-CH_2-COOH$,which contains three carboxyl groups,making it a tricarboxylic acid.
$2$. Malonic acid $(HOOC-CH_2-COOH)$ is a dicarboxylic acid.
$3$. Oxalic acid $(HOOC-COOH)$ is a dicarboxylic acid.
$4$. Glutaric acid $(HOOC-(CH_2)_3-COOH)$ is a dicarboxylic acid.
Therefore,citric acid is not a dicarboxylic acid.

(A) Citric acid is a tricarboxylic acid found in citrus fruits like lemon and orange.

(A) The chemical structure of citric acid is $HOOC-CH_2-C(OH)(COOH)-CH_2-COOH$.
By observing the structure,we can identify the functional groups present:
$1$. There is one alcoholic $-OH$ group attached to the central carbon atom.
$2$. There are three carboxylic acid $-COOH$ groups present in the molecule.
Therefore,the number of alcoholic $-OH$ and $-COOH$ groups in citric acid are $1$ and $3$ respectively.

(B) dicarboxylic acid contains two carboxylic acid $(-COOH)$ groups.
$1$. Succinic acid is $HOOC-CH_2-CH_2-COOH$ (dicarboxylic acid).
$2$. Acrylic acid is $CH_2=CH-COOH$ (monocarboxylic acid).
$3$. Malonic acid is $HOOC-CH_2-COOH$ (dicarboxylic acid).
$4$. Phthalic acid is $C_6H_4(COOH)_2$ (dicarboxylic acid).
Therefore,Acrylic acid is not a dicarboxylic acid.

(A) Citric acid is a tricarboxylic acid because it contains three carboxylic acid $(-COOH)$ groups in its structure.
Its chemical formula is $C_6H_8O_7$ or $HOOC-CH_2-C(OH)(COOH)-CH_2-COOH$.
Malonic acid is a dicarboxylic acid $(HOOC-CH_2-COOH)$.
Succinic acid is a dicarboxylic acid $(HOOC-CH_2-CH_2-COOH)$.
Malic acid is a dicarboxylic acid $(HOOC-CH_2-CH(OH)-COOH)$.

(B) Citric acid,also known as $2$-hydroxypropane-$1,2,3$-tricarboxylic acid,contains three carboxylic acid groups $(-COOH)$.
Therefore,it is a tricarboxylic acid.