Nomenclature of organic compounds Questions in English

(D) The given compound is $CH_3CH_2OCH(CH_3)_2$.
In $IUPAC$ nomenclature for ethers,the smaller alkyl group is treated as an alkoxy substituent attached to the longer alkane chain.
Here,the ethoxy group $(-OCH_2CH_3)$ is attached to the second carbon of the propane chain.
Therefore,the correct $IUPAC$ name is $2-$ethoxypropane.

(B) The given structure is $CH_3-C(CH_3)_2-CH=C(CH_3)_2$.
To determine the $IUPAC$ name,we identify the longest carbon chain containing the double bond.
Numbering the chain from the end closer to the double bond (right to left) gives the double bond position at $C-2$.
The methyl groups are located at positions $2, 4,$ and $4$.
Thus,the correct $IUPAC$ name is $2,4,4-Trimethylpent-2-ene$.

(C) $1$. Identify the principal functional group: The ester group $(-COOCH_3)$ has higher priority than the hydroxyl group $(-OH)$. Therefore,the parent chain is a benzoate ester.
$2$. Number the ring: The carbon atom of the benzene ring attached to the ester group is assigned position $1$.
$3$. Locate substituents: The hydroxyl group $(-OH)$ is attached to the carbon at position $3$ of the benzene ring.
$4$. Name the compound: The ester part is 'methyl' and the substituted benzene ring is '$3$-hydroxybenzoate'. Combining these,the $IUPAC$ name is Methyl $3-$hydroxybenzoate.

(C) The given structure is $CH_2=CH-O-CHO$.
This is an ester of formic acid $(HCOOH)$ and vinyl alcohol $(CH_2=CHOH)$.
In $IUPAC$ nomenclature for esters,the alkyl group attached to the oxygen is named first,followed by the name of the acid part with the suffix $-oate$.
The alkyl group is $CH_2=CH-$,which is called 'ethenyl' (or 'vinyl').
The acid part is $HCOO-$,which is derived from methanoic acid,so it is named 'methanoate'.
Combining these,the $IUPAC$ name is 'ethenyl methanoate'.

(B) According to $IUPAC$ nomenclature rules for cyclic compounds containing a double bond,the double bond carbons must be assigned positions $1$ and $2$ such that the substituents get the lowest possible locants.
$A$: In $3,6$-dimethylcyclohexene,the double bond is between $C1$ and $C2$. If we number the ring starting from the double bond,the substituents are at positions $3$ and $6$. This is correct.
$B$: In $1,6$-dimethylcyclohexene,the double bond is between $C1$ and $C2$. If we number the ring starting from the double bond,the substituents are at positions $1$ and $6$. This is correct.
$C$: In $6,6$-dimethylcyclohexene,the double bond is between $C1$ and $C2$. If we number the ring starting from the double bond,the substituents are at position $6$. This is correct.
$D$: In $1,5$-dimethylcyclohexene,the double bond is between $C1$ and $C2$. If we number the ring starting from the double bond,the substituents are at positions $1$ and $5$. This is correct.
Wait,let us re-evaluate the numbering for $B$. In $1,6$-dimethylcyclohexene,if we number the double bond as $1$ and $2$,the substituents are at $1$ and $6$. However,if we number in the other direction,we could get $1,2$-dimethylcyclohexene. Actually,for $B$,the structure shows a methyl group on one of the double-bonded carbons $(C1)$ and another methyl group on the adjacent carbon $(C6)$. This is correctly named $1,6$-dimethylcyclohexene.
Let us re-evaluate $A$: $3,6$-dimethylcyclohexene. If we number the double bond as $1,2$,the substituents are at $3$ and $6$. This is correct.
Actually,all these names follow the rules. Let us check if any structure is misnamed. In $B$,the structure is $1,6$-dimethylcyclohexene. This is correct. In $A$,$3,6$-dimethylcyclohexene is correct. In $C$,$6,6$-dimethylcyclohexene is correct. In $D$,$1,5$-dimethylcyclohexene is correct.
Upon closer inspection of standard $IUPAC$ rules,the numbering should be such that the sum of locants is minimized. For $B$,$1,6$-dimethylcyclohexene,the locants are $1,6$. If we number the other way,it is $1,2$-dimethylcyclohexene. Since $1,2 < 1,6$,the name $1,6$-dimethylcyclohexene is incorrect and should be $1,2$-dimethylcyclohexene.

(C) The functional groups present in the given compound are:
$1$. Aldehyde $(-CHO)$
$2$. Amine $(-NH_2)$
$3$. Ketone $(>C=O)$
$4$. Amide $(-CONH-)$
$5$. Carboxylic acid $(-COOH)$
$6$. Acid anhydride $(-CO-O-CO-)$
Thus,there are $6$ distinct functional groups present in the molecule.

(C) The parent chain is nonane,which contains $9$ carbon atoms.
At the $5^{th}$ position,there is a $2,2-\text{dimethylpropyl}$ group (also known as a neopentyl group).
The structure consists of a $9$-carbon chain with a substituent at the $5^{th}$ carbon.
The substituent is $-CH_2-C(CH_3)_3$.
Thus,the full structure is $CH_3-CH_2-CH_2-CH_2-CH(CH_2-C(CH_3)_3)-CH_2-CH_2-CH_2-CH_3$,which can be written as $CH_3-C(CH_3)_2-CH_2-CH(C_4H_9)-C_4H_9$.

(D) To determine the correct $IUPAC$ name,we must identify the longest carbon chain and number it such that substituents get the lowest possible locants.
$1$. For option $A$: The structure $4-(1, 1-$dimethylethyl$)-2-$methylpentane corresponds to a chain that is not the longest. The longest chain would be a heptane derivative.
$2$. For option $B$: $1-$aminobutan$-1-$one is not a valid $IUPAC$ name for the structure shown (which is butanamide).
$3$. For option $C$: $2-$ethyl$-3-$methylpentane is incorrect because the longest chain is actually a hexane chain ($3, 4-$dimethylhexane).
$4$. For option $D$: $3-$ethyl$-2-$methylpentane is a correct $IUPAC$ name for the structure shown in the image,as it correctly identifies the longest chain (pentane) and the positions of the substituents ($2-$methyl and $3-$ethyl).

(A) To determine the longest chain for $IUPAC$ nomenclature,we must include the principal functional group (ketone) and the double bond if possible.
Starting from the right end to give the ketone the lowest possible locant,the numbering is as follows:
$1$ (terminal $CH_3$),$2$ $(CH_2)$,$3$ $(C=O)$,$4$ $(CH_2)$,$5$ $(CH_2)$,$6$ $(C=)$,$7$ $(CH)$,$8$ $(CH_3)$.
The longest carbon chain contains $8$ carbon atoms.

(D) $1$. Identify the principal functional group: The carboxylic acid group $(-COOH)$ has the highest priority and is attached to the ring,so the parent name will end in $cyclohexanecarboxylic$ $acid$.
$2$. Number the ring: Start numbering from the carbon atom attached to the $-COOH$ group as $C-1$. To give the lowest possible locants to the double bond,hydroxyl group,and cyano group,we number the ring in a counter-clockwise direction.
$3$. Assign locants: The double bond starts at $C-2$,the hydroxyl group $(-OH)$ is at $C-3$,and the cyano group $(-CN)$ is at $C-5$.
$4$. Assemble the name: The substituents are $5-$cyano and $3-$hydroxy. The double bond is at position $2$. Combining these,we get $5-$cyano$-3-$hydroxycyclohex$-2-$enecarboxylic acid.

(C) Let us evaluate the given names:
$A$: The structure is $C_6H_5-CH_2-COOH$. The $IUPAC$ name is $2-$phenylacetic acid or $2-$phenylethanoic acid. This is correct.
$B$: The structure is $NH_2-CH_2-CH=CH_2$. The numbering starts from the carbon attached to the amine group. The name is $\text{prop}-2-\text{en}-1-\text{amine}$. This is correct.
$C$: The structure is a cyclohexane ring with a $-CHO$ group and a $-CH_3$ group at the $3-$position. When the $-CHO$ group is attached to a ring,the suffix used is $\text{carbaldehyde}$. Thus,the name is $3-$methylcyclohexanecarbaldehyde. The name '$3-$methylcyclohexanal' is incorrect.
$D$: The structure is $(CH_3)_2C=CHCOCH_3$. Numbering from the ketone end gives $4-\text{methylpent}-3-\text{en}-2-\text{one}$. This is correct.
Therefore,option $C$ has the incorrect $IUPAC$ name.

(C) The correct match is Phthaldehyde $\to$ benzene$-1, 2-$dicarbaldehyde.
$1.$ Acetanilide is $N-$phenylethanamide.
$2.$ Phenetole is ethoxybenzene.
$3.$ Acrolein is prop$-2-$enal.
$4.$ Phthaldehyde (or phthalaldehyde) is benzene$-1, 2-$dicarbaldehyde.

(B) $1$. Identify the principal functional group: The carboxylic acid group $(-COOH)$ has the highest priority and is attached to the ring,so the parent name is cyclohexanecarboxylic acid.
$2$. Number the ring: Start numbering from the carbon attached to the $-COOH$ group as $C-1$.
$3$. Assign positions to other substituents: The ketone group $(=O)$ is at position $2$ and the formyl group $(-CHO)$ is at position $4$.
$4$. Combine the names: The substituents are $4-$formyl and $2-$oxo. Arranging them alphabetically,we get $4-$formyl$-2-$oxocyclohexanecarboxylic acid.

(C) $1$. Identify the principal functional group: The hydroxyl group $(-OH)$ has higher priority than the double bond. Therefore,the suffix is $-ol$ and the carbon attached to $-OH$ is assigned position $1$.
$2$. Number the ring: Start numbering from the carbon attached to the $-OH$ group $(C-1)$. Proceed in the direction that gives the double bond the lowest possible locant. Moving towards the double bond,the double bond starts at $C-2$. Thus,the ring is a cyclohex$-2-$ene derivative.
$3$. Identify substituents: There is an ethyl group $(-CH_2CH_3)$ attached at position $3$.
$4$. Combine: The name is $3-$ethylcyclohex$-2-$en$-1-$ol.

(A) The given structure is a diene. According to $IUPAC$ nomenclature rules,the principal carbon chain must include the maximum number of multiple bonds (double bonds in this case).
Counting the carbon atoms in the longest chain containing both double bonds:
Starting from the left end,the chain consists of $7$ carbon atoms in a continuous sequence.
Therefore,the number of carbon atoms in the principal carbon chain is $7$.

(B) The chemical formula for crotonic acid is $CH_3-CH=CH-COOH$.
In the $IUPAC$ nomenclature,the longest carbon chain containing the carboxylic acid group is selected.
The chain has $4$ carbon atoms,so the parent alkane is butane.
The double bond starts at the $C-2$ position.
Therefore,the $IUPAC$ name is $But-2-enoic$ acid.

(C) The correct $IUPAC$ name for $CH_3-CH=CH-C \equiv CH$ is $Pent-3-en-1-yne$.
According to $IUPAC$ rules,when both double and triple bonds are present,numbering starts from the end that gives the lower locant to the multiple bonds.
If the locants are the same from both ends,the double bond is given priority for the lower number.
In this case,numbering from the right gives the double bond position $3$ and the triple bond position $1$ ($1,3$-combination),whereas numbering from the left gives $2$ and $4$ ($2,4$-combination).
Therefore,$Pent-3-en-1-yne$ is the correct name,making option $C$ the incorrectly matched one.

(C) An asymmetric carbon (chiral center) is a carbon atom bonded to four different groups.
$A$. In $1$-chloro-$2$-bromocyclopropane,the carbons at positions $1$ and $2$ are bonded to four different groups (e.g.,$C_1$ is bonded to $H$,$Cl$,$C_2$,and $C_3$),so it has asymmetric carbons.
$B$. In $2$-methylazetidine,the carbon at position $2$ is bonded to $H$,$CH_3$,$N$,and $C_3$,making it an asymmetric carbon.
$C$. In $C_2H_2ClBr$ (which is $CH_2Cl-CH_2Br$ or $CHCl=CHBr$),there is no carbon atom bonded to four different groups. For example,in $1$-bromo-$2$-chloroethane $(CH_2Cl-CH_2Br)$,each carbon is bonded to two $H$ atoms,which are identical.
$D$. In $3$-chlorobutane $(CH_3-CH_2-CHCl-CH_3)$,the carbon at position $3$ is bonded to $H$,$Cl$,$CH_3$,and $CH_2CH_3$,which are four different groups,so it is an asymmetric carbon.
Therefore,the molecule that does not have an asymmetric carbon is $C_2H_2ClBr$.

(C) $1$. Identify the longest carbon chain containing both the double bond and the triple bond. The chain has $6$ carbon atoms,so the parent alkane is hexane.
$2$. Number the chain from the end that gives the lower locant to the multiple bonds. Numbering from the left gives the double bond at $C-2$ and the triple bond at $C-5$. Numbering from the right gives the triple bond at $C-1$ and the double bond at $C-4$.
$3$. According to $IUPAC$ rules,if both double and triple bonds are present,the double bond is given priority for the lower number if there is a choice. However,the rule states we choose the set of locants that is lower. Comparing $(2, 5)$ and $(1, 4)$,the set $(1, 4)$ is lower.
$4$. Therefore,the correct numbering starts from the right: $C-1$ is the triple bond,$C-4$ is the double bond.
$5$. The name is constructed as $Hex-4-en-1-yne$.

(C) The given compound is an amide.
The parent chain is the cyclohexane ring attached to the carbonyl carbon,which is named as cyclohexanecarboxamide.
$A$ phenyl group $(-C_6H_5)$ is attached to the nitrogen atom of the amide group.
Therefore,the $IUPAC$ name is $N$-phenylcyclohexanecarboxamide.

(A) The $-CHO$ group consists of one Carbon atom,one Hydrogen atom,and one Oxygen atom.
Atomic number of Carbon $(C)$ = $6$ (Number of electrons = $6$)
Atomic number of Hydrogen $(H)$ = $1$ (Number of electrons = $1$)
Atomic number of Oxygen $(O)$ = $8$ (Number of electrons = $8$)
Total number of electrons = $6 + 1 + 8 = 15$.

(C) The given structure is a secondary amide where a phenyl group $(-C_6H_5)$ is attached to the nitrogen atom and a cyclohexane ring is attached to the carbonyl carbon.
According to $IUPAC$ nomenclature for amides,the parent chain is the one containing the carbonyl group. Here,it is a cyclohexane ring attached to a carboxamide group,making it a cyclohexane carboxamide.
The substituent on the nitrogen atom is a phenyl group,denoted as $N$-phenyl.
Combining these,the $IUPAC$ name is $N$-phenylcyclohexanecarboxamide.

(B) The given compound is $CH_3-CH=CH-COOC_2H_5$.
It is an ester.
The alkyl group attached to the oxygen atom is an ethyl group $(C_2H_5)$.
The parent acid chain contains $4$ carbon atoms,and the double bond starts at the $2^{nd}$ carbon position.
Therefore,the $IUPAC$ name is Ethyl $2-$butenoate.

(A) $1$. Identify the longest carbon chain containing the double bond. The chain has $6$ carbon atoms,so the parent alkane is hexane,and with the double bond at position $1$,it is hex$-1-$ene.
$2$. Number the chain starting from the end that gives the double bond the lowest possible locant. Thus,the double bond starts at $C-1$.
$3$. Identify the substituents: a bromo group $(-Br)$ is at $C-5$ and a chloro group $(-Cl)$ is at $C-3$.
$4$. Arrange the substituents in alphabetical order: Bromo comes before Chloro.
$5$. Combining these,the name is $5-$Bromo$-3-$chlorohex$-1-$ene.

(B) The given structure is a cyclic anhydride formed from succinic acid $(butanedioic \ acid)$.
In the structure,there are four carbon atoms in the main chain (including the two carbonyl carbons).
The parent dicarboxylic acid is $butanedioic \ acid$.
When it forms a cyclic anhydride,the name is derived by replacing 'acid' with 'anhydride'.
Thus,the $IUPAC$ name is $butanedioic \ anhydride$ (also commonly known as succinic anhydride).

(C) $1$. The principal functional group is the nitrile group $(-CN)$,so it is assigned the lowest possible number,$C-1$.
$2$. The parent carbon chain must include the $-CN$ carbon and the double bond. The longest chain containing these is a $5$-carbon chain (pentene derivative).
$3$. Numbering: $C^1(N) - C^2H(CH_3) - C^3H(CH_2CH_3) - C^4H = C^5H_2$.
$4$. Substituents: $A$ methyl group at $C-2$ and an ethyl group at $C-3$.
$5$. Alphabetical order: Ethyl comes before Methyl.
$6$. The correct $IUPAC$ name is $3-$ Ethyl $-2-$ methylpent $-4-$ ene $-1-$ nitrile.

(D) All the given matches are incorrect according to $IUPAC$ nomenclature rules:
$(A)$ For the structure $CH_2=CH-CH(Br)-CH_3$,the correct $IUPAC$ name is $3-$bromobut$-1-$ene (the double bond has priority over the halogen).
$(B)$ For the structure $CH_2=CH-CH_2-OCH_3$,the correct $IUPAC$ name is $3-$methoxyprop$-1-$ene (the double bond has priority over the ether group).
$(C)$ For the structure $CH_3-C(CH_3)(OH)-CH_3$,the correct $IUPAC$ name is $2-$methylpropan$-2-$ol.

(C) The longest carbon chain containing the double bond has $4$ carbon atoms,making the parent chain 'butene'.
Numbering starts from the end closer to the double bond to give it the lowest possible number $(1)$.
$A$ methyl substituent is located at the $3^{rd}$ carbon.
Therefore,the $IUPAC$ name is $3-methylbut-1-ene$.

(B) The correct answer is $(B)$.
According to $IUPAC$ nomenclature rules,when three or more identical carbon-containing functional groups (like $-CN$) are attached to the same parent chain,the carbon atoms of these functional groups are excluded from the main chain.
In the compound $NC-CH_2-CH(CN)-CH_2-CN$,the main chain consists of $3$ carbon atoms (propane).
The suffix used for the $-CN$ group in this specific situation is 'carbonitrile'.
Therefore,the correct name is Propane$-1,2,3-$tricarbonitrile.

(B) $1$. Identify the longest carbon chain containing the maximum number of double bonds. The chain has $8$ carbon atoms (octa-).
$2$. Number the chain from the end that gives the lowest locants to the double bonds. Numbering from the right gives double bonds at positions $1, 3,$ and $6$.
$3$. The substituents are two methyl groups at positions $3$ and $7$.
$4$. Combining these,the name is $3,7-$Dimethyl octa$-1,3,6-$triene.

(B) chiral carbon is a carbon atom bonded to four different groups.
$1$. $2, 2-$ Dimethyl $-1, 3-$ dibromo hexane: The carbon at position $3$ is bonded to $-H, -Br, -CH_2-C(CH_3)_2-CH_3$ and $-CH_2-CH_2-CH_3$. Since all four groups are different,it is chiral.
$2$. Neopentyl chloride $(CH_3-C(CH_3)_2-CH_2-Cl)$: The central carbon is bonded to two identical $-CH_3$ groups,and the terminal carbon is bonded to two identical $-H$ atoms. No carbon is bonded to four different groups. Thus,it is achiral.
$3$. $2-$ Chloro butane $(CH_3-CHCl-CH_2-CH_3)$: The carbon at position $2$ is bonded to $-H, -Cl, -CH_3$ and $-CH_2-CH_3$. It is chiral.
$4$. $2-$ Pentanol $(CH_3-CH(OH)-CH_2-CH_2-CH_3)$: The carbon at position $2$ is bonded to $-H, -OH, -CH_3$ and $-CH_2-CH_2-CH_3$. It is chiral.
Therefore,Neopentyl chloride does not contain a chiral carbon.

(D) The question asks for the incorrect $IUPAC$ name.
$1$. For $CH_3-CH(OH)-CH_2-CH_3$,the $IUPAC$ name is $2-$Butanol,not $2-$Hydroxybutane.
$2$. For $CH_3-CH_2-Cl$,the $IUPAC$ name is Chloroethane,not Ethyl chloride (which is a common name).
$3$. For $(C_2H_5)_2NH$,the $IUPAC$ name is $N-$Ethylethanamine,not Diethylamine (which is a common name).
Since all options provided are either common names or incorrect $IUPAC$ nomenclature,all are incorrect as $IUPAC$ names.

(C) The functional groups present are nitrile $(-CN)$ and ketone $( > C=O)$.
According to $IUPAC$ priority rules,the nitrile group has higher priority than the ketone group.
The principal functional group is nitrile,and the ketone is treated as a substituent (oxo).
Numbering starts from the nitrile carbon as $C1$.
The parent chain has $5$ carbons (pentanenitrile).
There are two methyl groups at $C2$ and an oxo group at $C4$.
Thus,the name is $2,2-$dimethyl$-4-$oxopentanenitrile.

(B) The $IUPAC$ name $4-bromo-3-methylbut-1-ene$ indicates a $4$-carbon chain $(but)$ with a double bond at position $1$ $(but-1-ene)$.
At position $3$,there is a methyl group $(-CH_3)$,and at position $4$,there is a bromine atom $(-Br)$.
Constructing the chain: $C1(H_2)=C2(H)-C3(H)(CH_3)-C4(H_2)Br$.
Thus,the correct structure is $CH_2=CH-CH(CH_3)-CH_2Br$.

(C) $1$. Identify the longest carbon chain. The longest chain in the given structure contains $7$ carbon atoms (heptane).
$2$. Number the chain from the end that gives the lowest locants to the substituents. Numbering from right to left gives the substituents at positions $2, 3, 4,$ and $5$.
$3$. The substituents are three methyl groups at positions $2, 3,$ and $5$,and a propyl group at position $4$.
$4$. Combining these,the correct $IUPAC$ name is $2,3,5-$trimethyl$-4-$propylheptane.

(A) In the structure $CH_3-C(=O)-CH(CH_3)-CH_3$,the principal functional group (ketone) should get the lowest possible number.
Numbering from the left,the ketone is at $C2$ and the methyl group is at $C3$.
Thus,the correct $IUPAC$ name is $3-$methyl$-2-$butanone.
$(d)$ In $CH_3-CH(Cl)-CH(Br)-CH_3$,the alphabetical order should be followed for substituents.
$B$ (bromo) comes before $C$ (chloro).
Thus,the correct $IUPAC$ name is $2-$bromo$-3-$chlorobutane.

(D) $1$. Identify the longest carbon chain. The longest chain in the given structure contains $8$ carbon atoms,so the parent alkane is octane.
$2$. Number the chain from the end that gives the lowest locants to the substituents.
$3$. Numbering from left to right gives substituents at positions $3$ and $4$. Numbering from right to left gives substituents at positions $5$ and $6$.
$4$. Following the lowest locant rule,we number from left to right.
$5$. At position $3$,there is a methyl group $(-CH_3)$,and at position $4$,there is an ethyl group $(-CH_2CH_3)$.
$6$. According to $IUPAC$ rules,substituents are listed in alphabetical order. Therefore,ethyl comes before methyl.
$7$. The correct name is $4-$ethyl$-3-$methyloctane.

(D) $1$. Identify the longest carbon chain containing both double bonds,which consists of $10$ carbon atoms (decadiene).
$2$. Number the chain from the end that gives the lowest locants to the double bonds and substituents.
$3$. Numbering from left to right: $CH_3(1)-CH(CH_3)(2)-CH_2(3)-CH(4)=CH(5)-CH(6)=CH(7)-CH(CH_3)(8)-CH_2(9)-CH_3(10)$.
$4$. The double bonds are at positions $4$ and $6$,and methyl groups are at positions $2$ and $8$.
$5$. Therefore,the $IUPAC$ name is $2,8-$ dimethyl $-4,6-$ decadiene.

(N/A) The condensed formula $CH_3-CH_2-CO-CH_2-CH_3$ represents pentan-$3$-one. Its complete structural formula is:
$H-C(H)(H)-C(H)(H)-C(=O)-C(H)(H)-C(H)(H)-H$
$(b)$ The condensed formula $CH_3-CH=CH-CH_2-CH_2-CH_2-CH_3$ represents hept-$2$-ene. Its complete structural formula is:
$H-C(H)(H)-C(H)=C(H)-C(H)(H)-C(H)(H)-C(H)(H)-C(H)(H)-H$

(N/A) Condensed formula:
$(a)$ $HO(CH_{2})_{3}CH(CH_{3})CH(CH_{3})_{2}$
$(b)$ $HOCH(CN)_{2}$
Bond-line formula:
$(a)$ $A$ chain of $6$ carbons with an $-OH$ group at the first carbon,a methyl group at the $4^{th}$ carbon,and a methyl group at the $5^{th}$ carbon.
$(b)$ $A$ central carbon atom bonded to an $-OH$ group and two $-CN$ groups.

(N/A) To expand bond-line formulas,replace each vertex and terminal point with a carbon atom and add the appropriate number of hydrogen atoms to satisfy the tetravalency of carbon.
$(a)$ The structure is isopropylcyclohexane. The expanded form shows a cyclohexane ring with an isopropyl group attached at one position.
$(b)$ The structure is octane $(CH_3-CH_2-CH_2-CH_2-CH_2-CH_2-CH_2-CH_3)$.
$(c)$ The structure is but$-3-$yn$-2-$ol $(HC \equiv C-CH_2-CH(OH)-CH_3)$.
$(d)$ The structure is $2,3-$dimethylbutane $((CH_3)_2CH-CH(CH_3)_2)$.

(A) According to the lowest locant rule,the set of locants $2,5,6$ is lower than $3,4,7$. Therefore,$2,5,6-$trimethyloctane is the correct name.
$(b)$ When substituents are at equivalent positions from either end of the chain,the lower number is assigned to the substituent that comes first in the alphabetical order. Since $E$ (Ethyl) comes before $M$ (Methyl),the name $3-$ethyl$-5-$methylheptane is correct.

(N/A) $(i)$ The functional group present is an alcohol $(-OH)$. The longest chain containing $-OH$ has $8$ carbon atoms. The $-OH$ is on carbon atom $3$ and a methyl group is at carbon $6$. The name is $6-$Methyloctan$-3-$ol.
$(ii)$ The functional group is ketone $(>C=O)$. Two keto groups are at carbons $2$ and $4$. The longest chain has $6$ carbon atoms. The name is Hexane$-2,4-$dione.
$(iii)$ The principal functional group is carboxylic acid $(-COOH)$. The keto group is at carbon $5$. The longest chain has $6$ carbon atoms. The name is $5-$Oxohexanoic acid.
$(iv)$ Two $C=C$ double bonds are at carbons $1$ and $3$,and one $C \equiv C$ triple bond is at carbon $5$. The longest chain has $6$ carbon atoms. The name is Hexa$-1,3-$dien$-5-$yne.

(N/A) $(i)$ 'hexane' indicates the presence of $6$ carbon atoms in the chain. The functional group chloro is present at carbon $2$. Hence,the structure is $CH_3-CH_2-CH_2-CH_2-CH(Cl)-CH_3$.
$(ii)$ 'pent' indicates that the parent hydrocarbon contains $5$ carbon atoms. 'en' and 'ol' correspond to the functional groups $C=C$ and $-OH$ at carbon atoms $4$ and $2$ respectively. Thus,the structure is $CH_2=CH-CH_2-CH(OH)-CH_3$.
$(iii)$ $A$ six-membered ring containing a carbon-carbon double bond is implied by cyclohexene. The prefix $3-$nitro means that a nitro group is present on $C-3$. The double bond gets preference over the $-NO_2$ group. The structure is a cyclohexene ring with a double bond between $C-1$ and $C-2$ and a $-NO_2$ group at $C-3$.
$(iv)$ '$1-$ol' means that a $-OH$ group is present at $C-1$. The $-OH$ group is the principal functional group and gets preference over the $C=C$ bond. Thus,the structure is a cyclohexene ring with $-OH$ at $C-1$ and the double bond between $C-2$ and $C-3$.
$(v)$ 'heptanal' indicates an aldehyde containing $7$ carbon atoms. The '$6-$hydroxy' indicates that an $-OH$ group is present at carbon $6$. Thus,the structural formula is $CH_3-CH(OH)-CH_2-CH_2-CH_2-CH_2-CHO$.

(N/A) $o-$Ethylanisole: $A$ benzene ring with a methoxy group $(-OCH_3)$ at position $1$ and an ethyl group $(-C_2H_5)$ at position $2$.
$(b)$ $p-$Nitroaniline: $A$ benzene ring with an amino group $(-NH_2)$ at position $1$ and a nitro group $(-NO_2)$ at position $4$.
$(c)$ $2,3-$Dibromo$-1-$phenylpentane: $A$ pentane chain with a phenyl group $(-C_6H_5)$ at position $1$ and bromine atoms at positions $2$ and $3$. The structure is $C_6H_5-CH_2-CH(Br)-CH(Br)-CH_2-CH_3$.
$(d)$ $4-$Ethyl$-1-$fluoro$-2-$nitrobenzene: $A$ benzene ring with a fluorine atom at position $1$,a nitro group at position $2$,and an ethyl group at position $4$.

(N/A) The bond line formulas for the given compounds are as follows:
$(a)$ Isopropyl alcohol: $A$ $V$-shaped chain with an $-OH$ group attached to the central carbon.
$(b)$ $2,3-$Dimethylbutanal: $A$ four-carbon chain with an aldehyde group $(-CHO)$ at position $1$ and methyl groups at positions $2$ and $3$.
$(c)$ Heptan$-4-$one: $A$ seven-carbon chain with a ketone group $(C=O)$ at position $4$.

(N/A) $1-phenylpropane$ (Note: The provided solution image incorrectly labels it as $3-phenylpropane$)
$(b)$ $3-methylpentanenitrile$ (Note: The provided solution image incorrectly labels it as $2-methyl-1-cyanobutane$)
$(c)$ $2,5-dimethylheptane$
$(d)$ $3-bromo-3-chloroheptane$
$(e)$ $3-chloropropanal$
$(f)$ $2,2-dichloroethanol$ (Note: The provided solution image incorrectly labels it as $1,1-dichloro-2-ethanol$)

(A, B, C, D) The $IUPAC$ nomenclature rules dictate the following:
$(a)$ The prefix $di-$ indicates two identical substituents. Since two methyl groups are at $C-2$,the correct name is $2,2-$ dimethylpentane.
$(b)$ According to the lowest locant rule,the set $2,4,7$ is preferred over $2,5,7$. Thus,the correct name is $2,4,7-$ trimethyloctane.
$(c)$ When substituents are at equivalent positions,alphabetical priority determines the numbering. $Chloro$ comes before $methyl$,so $2-$ chloro$-4-$methylpentane is correct.
$(d)$ The alcohol group $(-OH)$ has higher priority than the alkyne group $(-C \equiv C-)$. The chain is numbered to give the principal functional group the lowest possible number. Thus,the correct name is But$-3-$yn$-1-$ol.