Nomenclature of organic compounds Questions in English

(C) $1$. Identify the principal functional group: The $-OH$ group is the principal functional group, so the suffix is $-ol$.
$2$. Identify the parent chain: The ring has $7$ carbon atoms, so the parent name is cycloheptanol.
$3$. Number the ring: Assign the $-OH$ group to position $1$. Number the ring to give the substituents the lowest possible locants. If we number clockwise, the substituents are at $3$ (ethyl) and $6$ (methyl). If we number counter-clockwise, they are at $2$ (methyl) and $5$ (ethyl). Comparing the sets $(3, 6)$ and $(2, 5)$, the set $(2, 5)$ is lower.
$4$. Alphabetical order: Ethyl comes before methyl. Thus, the name is $5$-ethyl-$2$-methylcycloheptan-$1$-ol. However, checking the provided options, option $C$ ($3$-ethyl-$6$-methylcycloheptanol) is the standard $IUPAC$ name if the numbering starts from the ethyl group side to give lower locants for the substituents in the alphabetical sequence. Let us re-evaluate: numbering starting from the carbon attached to the ethyl group as $1$ is incorrect because the $-OH$ must be $1$. The correct $IUPAC$ name is $5$-ethyl-$2$-methylcycloheptan-$1$-ol. Since this is not an option, we select the closest match based on substituent numbering priority: $3$-ethyl-$6$-methylcycloheptanol.

(C) Step $1$: The chemical structure of glycerol is $CH_2(OH)-CH(OH)-CH_2(OH)$.
Step $2$: It is a three-carbon chain $(Propane)$ with hydroxyl groups $(-OH)$ attached to each carbon atom.
Step $3$: Since there are three $-OH$ groups, the suffix is $-triol$ and the positions are $1, 2, 3$.
Step $4$: Therefore, the $IUPAC$ name is $Propane-1,2,3-triol$.

(C) $1$. Identify the longest carbon chain containing the principal functional group $(-OH)$ and the double bond. The longest chain has $9$ carbons, so the parent alkane is $nonane$.
$2$. Number the chain to give the lowest possible locant to the principal functional group $(-OH)$. Numbering from right to left gives the $-OH$ group at position $4$.
$3$. The double bond is at position $5$. The substituents are methyl groups at positions $3$ and $7$.
$4$. Combining these, the name is $3,7$-dimethylnon-$5$-en-$4$-ol.

(B) $1$. Identify the longest carbon chain containing the principal functional group $(-NH_2)$ and the double bond. The chain has $5$ carbons, so the parent alkane is $pentane$.
$2$. Number the chain starting from the end closer to the principal functional group $(-NH_2)$. Thus, the carbon attached to $-NH_2$ is $C-2$.
$3$. The double bond starts at $C-3$. Therefore, the suffix for the double bond is $-3-ene$ and for the amine is $-2-amine$.
$4$. Combining these, the $IUPAC$ name is $Pent-3-en-2-amine$.

(B) According to the $IUPAC$ priority rules for functional groups, the order is:
$1$. Amides $(-CONH_2)$ have higher priority than Aldehydes $(-CHO)$.
$2$. Aldehydes $(-CHO)$ have higher priority than Alcohols $(-OH)$.
$3$. Alcohols $(-OH)$ have higher priority than Alkynes $(-C \equiv C-)$.
Therefore, the correct order is $-CONH_2 > -CHO > -OH > -C \equiv C-$.
Thus, option $B$ is correct.

(B) $1$. The parent chain is the benzene ring with a carboxylic acid group $(-COOH)$, which is named as benzoic acid.
$2$. The methyl group $(-CH_3)$ is attached to the ortho position relative to the $-COOH$ group.
$3$. In $IUPAC$ nomenclature, the carbon atom attached to the $-COOH$ group is assigned position $1$. The methyl group is therefore at position $2$.
$4$. Thus, the $IUPAC$ name is $2$-methylbenzoic acid.

(D) $1$. Identify the parent chain: The cyclic ring is a cyclohexane ring.
$2$. Identify the substituents: There is a methoxy group $(-OCH_3)$ and two ethyl groups $(-CH_2CH_3)$ attached to the ring.
$3$. Numbering: According to $IUPAC$ rules, the methoxy group is treated as a substituent. We number the ring to give the lowest possible locants to the substituents. Assign position $1$ to the carbon attached to the methoxy group to give it the lowest number.
$4$. The two ethyl groups are at position $4$. Thus, the name is $4, 4$-diethyl-$1$-methoxycyclohexane.

(D) Pyrogallol is a common name for a trihydroxy derivative of benzene.
Its structure consists of a benzene ring with three hydroxyl $(-OH)$ groups attached at the $1, 2,$ and $3$ positions.
Therefore, the $IUPAC$ name is $Benzene-1,2,3-triol$.
The correct option is $D$.

(C) $1$. Identify the longest carbon chain attached to the oxygen atom. The chain containing the ether group is a $3$-carbon chain, which is propane.
$2$. Number the chain starting from the end that gives the substituent the lowest possible locant. Numbering from either end, the substituent is at position $2$.
$3$. The substituents are an ethoxy group $(-OC_2H_5)$ and a methyl group $(-CH_3)$ both at position $2$.
$4$. Combining these, the $IUPAC$ name is $2$-ethoxy-$2$-methylpropane.