Introduction of Halogen containing compounds Questions in English

(N/A) Halogen compounds are classified based on the number of halogen atoms and the hybridization of the carbon atom to which the halogen is attached:
$1$. Based on the number of halogen atoms:
$(i)$ Monohalides: Contain one halogen atom.
(ii) Dihalides: Contain two halogen atoms.
(iii) Trihalides: Contain three halogen atoms.
(iv) Polyhalides: Contain more than three halogen atoms.
$2$. Based on the hybridization of the carbon atom ($sp^3$ $C-X$ bond):
$(a)$ Alkyl halides: Classified as primary $(1^\circ)$,secondary $(2^\circ)$,or tertiary $(3^\circ)$ based on the carbon atom attached to the halogen.
$(b)$ Allylic halides: The halogen is attached to an $sp^3$ hybridized carbon atom next to a carbon-carbon double bond $(C=C-C-X)$.
$(c)$ Benzylic halides: The halogen is attached to an $sp^3$ hybridized carbon atom next to an aromatic ring $(Ar-CH_2-X)$.
$3$. Based on the hybridization of the carbon atom ($sp^2$ $C-X$ bond):
$(a)$ Vinylic halides: The halogen is attached directly to an $sp^2$ hybridized carbon atom of a double bond $(C=C-X)$.
$(b)$ Aryl halides: The halogen is attached directly to an $sp^2$ hybridized carbon atom of an aromatic ring $(Ar-X)$.

(N/A) The naming of alkyl halides is done as follows:
$1$. Common Names: These are named by naming the alkyl group followed by the name of the halide (e.g.,$n$-propyl bromide).
$2$. $IUPAC$ Names: These are named as halo-substituted alkanes. The halogen atom is treated as a substituent on the longest carbon chain,and its position is indicated by a number.
| Structural Formula | Common Name | $IUPAC$ Name |
| :--- | :--- | :--- |
| $CH_3CH_2CH_2Br$ | $n$-propyl bromide | $1$-bromopropane |
| $CH_3CH(Cl)CH_3$ | isopropyl chloride | $2$-chloropropane |
| $(CH_3)_2CHCH_2Cl$ | isobutyl chloride | $1$-chloro-$2$-methylpropane |
| $(CH_3)_3CCH_2Cl$ | neopentyl chloride | $1$-chloro-$2,2$-dimethylpropane |
| $CH_3CH(Br)CH_3$ | isopropyl bromide | $2$-bromopropane |

(N/A) Rules for nomenclature of aryl halides:
$(i)$ For monohalogen derivatives of benzene,the common and $IUPAC$ names are the same. In the $IUPAC$ system,prefixes $ortho- (o-)$,$meta- (m-)$,and $para- (p-)$ are replaced by $1,2-$,$1,3-$,and $1,4-$ respectively.
$(ii)$ If more than two halogen atoms are present in the ring,the $IUPAC$ system is used by numbering the ring positions $1, 2, 3, 4, 5, 6$ and using prefixes like $tri-$,$tetra-$,etc.
$(b)$ Examples:
| Structure | Common Name | $IUPAC$ Name |
| :--- | :--- | :--- |
| $C_6H_5Br$ | Bromobenzene | Bromobenzene |
| $C_6H_4Br_2$ $(o-)$ | $o$-Dibromobenzene | $1,2$-Dibromobenzene |
| $C_6H_4Br_2$ $(m-)$ | $m$-Dibromobenzene | $1,3$-Dibromobenzene |
| $C_6H_4Br_2$ $(p-)$ | $p$-Dibromobenzene | $1,4$-Dibromobenzene |
| $C_6H_3Br_3$ $(1,3,5-)$ | sym-Tribromobenzene | $1,3,5$-Tribromobenzene |
| $C_6H_3Br_3$ $(1,2,4-)$ | - | $1,2,4$-Tribromobenzene |

(N/A) Rules for naming aryl halides:
$(i)$ For monohaloarenes,the common and $IUPAC$ names are the same. In the $IUPAC$ system,the positions of substituents are indicated by numbering the carbon atoms of the ring starting from the carbon bearing the halogen atom.
$(ii)$ For dihaloarenes,the prefixes $ortho$ $(o-)$,$meta$ $(m-)$,and $para$ $(p-)$ are used in common names,while $1,2-$,$1,3-$,and $1,4-$ are used in the $IUPAC$ system.
$(iii)$ If more than two halogen atoms are present in the ring,the $IUPAC$ system is used by numbering the ring and using prefixes like $1,2,3-$,$1,3,5-$,etc.
$(b)$ Examples:

Structure	Common Name	$IUPAC$ Name
$C_6H_5Br$	Bromobenzene	Bromobenzene
$o-C_6H_4Br_2$	$o$-Dibromobenzene	$1,2$-Dibromobenzene
$m-C_6H_4Br_2$	$m$-Dibromobenzene	$1,3$-Dibromobenzene
$p-C_6H_4Br_2$	$p$-Dibromobenzene	$1,4$-Dibromobenzene
$C_6H_3Br_3$	Symmetrical tribromobenzene	$1,3,5$-Tribromobenzene
$C_6H_3Br_3$	-	$1,2,4$-Tribromobenzene

(N/A) Haloalkanes containing two identical halogen atoms are classified into two types based on the position of the halogen atoms:
$1$. Geminal Dihalides (Alkylidene dihalides):
- In these compounds,two halogen atoms are attached to the same carbon atom.
- Example: $CH_3-CHCl_2$ is named as Ethylidene chloride (common name) and $1,1-dichloroethane$ ($IUPAC$ name).
$2$. Vicinal Dihalides (Alkylene dihalides):
- In these compounds,two halogen atoms are attached to adjacent carbon atoms.
- Example: $Cl-CH_2-CH_2-Cl$ is named as Ethylene dichloride (common name) and $1,2-dichloroethane$ ($IUPAC$ name).

(N/A)

Structure	Common Name	$IUPAC$ Name
$CH_3CH_2CH(Cl)CH_3$	sec-Butyl chloride	$2$-Chlorobutane
$(CH_3)_3CCH_2Br$	Neopentyl bromide	$1$-Bromo-$2,2$-dimethylpropane
$(CH_3)_3CBr$	tert-Butyl bromide	$2$-Bromo-$2$-methylpropane
$CH_2=CHCl$	Vinyl chloride	Chloroethene
$CH_2=CHCH_2Br$	Allyl bromide	$3$-Bromopropene
$C_6H_4(Cl)(CH_3)$ (ortho)	$o$-Chlorotoluene	$1$-Chloro-$2$-methylbenzene or $2$-Chlorotoluene
$C_6H_5CH_2Cl$	Benzyl chloride	Chlorophenylmethane
$CH_2Cl_2$	Methylene chloride	Dichloromethane
$CHCl_3$	Chloroform	Trichloromethane
$CHBr_3$	Bromoform	Tribromomethane
$CCl_4$	Carbon tetrachloride	Tetrachloromethane
$CH_3CH_2CH_2F$	$n$-Propyl fluoride	$1$-Fluoropropane

(N/A) In halogen compounds, the carbon-halogen bond is polar: Halogen atoms are located on the right side of the periodic table. The electronegativity of all halogen atoms $(F, Cl, Br, I)$ is higher than that of the carbon atom. Due to this, the electrons of the carbon-halogen $(C-X)$ bond are shifted towards the halogen, causing the carbon to acquire a partial positive charge and the halogen to acquire a partial negative charge, making the $C-X$ bond polar.
$(b)$ Trends in polarity, bond length, and bond enthalpy from $C-F$ to $C-I$: As we move down the group in the periodic table, the size of the halogen atoms $(F, Cl, Br, I)$ increases. Fluorine is the smallest and iodine is the largest.
Therefore, the carbon-halogen bond length increases from $C-F$ to $C-I$. The bond length, bond enthalpy, and dipole moment of $C-X$ bonds in methyl halides $(CH_3X)$ are given in the table below:

Bond	Bond Length $(pm)$	$C-X$ Bond Enthalpy $(kJ \ mol^{-1})$	Dipole Moment $(Debye)$
$CH_3-F$	$139$	$452$	$1.847$
$CH_3-Cl$	$178$	$351$	$1.860$
$CH_3-Br$	$193$	$293$	$1.830$
$CH_3-I$	$214$	$234$	$1.636$

Order of bond length: $CH_3-F$ < $CH_3-Cl$ < $CH_3-Br$ < $CH_3-I$
Order of dipole moment: $CH_3-Cl$ > $CH_3-F$ > $CH_3-Br$ > $CH_3-I$

(N/A) The classification of alkyl halides is based on the nature of the carbon atom to which the halogen is attached.
$(i)$ $CH_3-CH=CH-CH_2Br$: The $Br$ atom is attached to a primary $(1^{\circ})$ carbon atom. Hence,it is a primary $(1^{\circ})$ halide.
$(ii)$ $CH_3-CH=CH-CH(Br)-CH_3$: The $Br$ atom is attached to a secondary $(2^{\circ})$ carbon atom. Hence,it is a secondary $(2^{\circ})$ halide.
$(iii)$ $(CH_3)_3C-Br$: The $Br$ atom is attached to a tertiary $(3^{\circ})$ carbon atom. Hence,it is a tertiary $(3^{\circ})$ halide.

(A-2, B-4, C-1, D-3) The classification of the given compounds is as follows:
$A$. $CH_3-CH(X)-CH_3$ is an alkyl halide (specifically,a secondary alkyl halide).
$B$. $CH_2=CH-CH_2-X$ is an allyl halide because the halogen is attached to an $sp^3$ hybridized carbon atom next to a carbon-carbon double bond.
$C$. $C_6H_5-X$ is an aryl halide because the halogen is directly attached to an aromatic ring.
$D$. $CH_2=CH-X$ is a vinyl halide because the halogen is directly attached to an $sp^2$ hybridized carbon atom of a double bond.
Therefore,the correct matching is: $A-2, B-4, C-1, D-3$.

(N/A) Vicinal dihalides are compounds in which two halogen atoms are attached to adjacent (neighboring) carbon atoms in the carbon chain.
Examples include:
$1$. $1,2-dibromopropane$ $(CH_3-CHBr-CH_2Br)$
$2$. $1,2-dichloroethane$ $(CH_2Cl-CH_2Cl)$

(A-3, B-1, C-2, D-4) The classification is based on the number of halogen atoms present in the molecule:
$(A)$ ${C_2}{H_5}X$ contains one halogen atom,so it is a Monohaloalkane $(3)$.
$(B)$ $C{H_2}X - C{H_2}X$ contains two halogen atoms,so it is a Dihaloalkane $(1)$.
$(C)$ $C{H_2}X - CHX - C{H_2}X$ contains three halogen atoms,so it is a Trihaloalkane $(2)$.
$(D)$ $C{X_4}$ contains four halogen atoms,so it is a Tetrahaloalkane $(4)$.
Therefore,the correct matching is: $(A-3, B-1, C-2, D-4)$.

(A) The classification is based on the number of halogen atoms attached to the aromatic ring:
$(A)$ The structure is a monohalo-substituted cyclic diene (monohaloarene): $(A \rightarrow iv)$.
$(B)$ The structure is a benzene ring with two halogen atoms at para positions (dihaloarene): $(B \rightarrow i)$.
$(C)$ The structure is a benzene ring with three halogen atoms (trihaloarene): $(C \rightarrow ii)$.
$(D)$ The structure is a benzene ring with one chlorine atom (monochloroarene): $(D \rightarrow v)$.

(A-IV, B-III, C-II, D-V) The classification is based on the carbon atom to which the halogen atom is attached:
$(A)$ $C_6H_5CH_2X$: The halogen is attached to a primary carbon atom adjacent to the benzene ring,which is a $1^{\circ}$ benzylic halide $(iv)$.
$(B)$ $C_6H_5CH(CH_3)X$: The halogen is attached to a secondary carbon atom adjacent to the benzene ring,which is a $2^{\circ}$ benzylic halide $(iii)$.
$(C)$ $C_6H_5C(CH_3)_2X$: The halogen is attached to a tertiary carbon atom adjacent to the benzene ring,which is a $3^{\circ}$ benzylic halide $(ii)$.
$(D)$ $C_6H_5X$: The halogen is directly attached to the benzene ring,which is an aryl halide $(v)$.
Therefore,the correct matching is: $(A$ $\rightarrow iv), (B$ $\rightarrow iii), (C$ $\rightarrow ii), (D$ $\rightarrow v)$.

(D) The classification of alkyl halides is based on the number of alkyl groups attached to the carbon atom bearing the halogen atom:
- $(A)$ $CH_3CH_2X$ is a primary $(1^{\circ})$ halide.
- $(B)$ $R'CH_2X$ is a primary $(1^{\circ})$ halide.
- $(C)$ $R'R''CHX$ is a secondary $(2^{\circ})$ halide.
- $(D)$ $R'R''CR'''X$ is a tertiary $(3^{\circ})$ halide.
Therefore,the correct matching is: $(A-4, B-4, C-3, D-2)$.

(A-III, B-IV, C-II, D-I) The classification of halides is based on the hybridization of the carbon atom attached to the halogen atom:
$A$. $CH_2=CHCH_2X$: The halogen is attached to an $sp^3$ hybridized carbon atom next to a carbon-carbon double bond,which is an allylic halide $(iii)$.
$B$. $CH_2=CHX$: The halogen is attached directly to an $sp^2$ hybridized carbon atom of a double bond,which is a vinylic halide $(iv)$.
$C$. $C_6H_5CH_2X$: The halogen is attached to an $sp^3$ hybridized carbon atom bonded to an aromatic ring,which is a benzylic halide $(ii)$.
$D$. $C_6H_5X$: The halogen is attached directly to an $sp^2$ hybridized carbon atom of an aromatic ring,which is an aryl halide $(i)$.
Therefore,the correct matching is: $(A-iii, B-iv, C-ii, D-i)$.

(A-III, B-II, C-III, D-II) To determine the hybridization of the carbon atom attached to the halogen:
$A$. $CH_3-CH_2-Cl$: The carbon attached to $Cl$ is bonded to one $C$ and two $H$ atoms (single bonds). It has $4$ sigma bonds,so it is $sp^3$ hybridized.
$B$. $CH_2=CH-Cl$: The carbon attached to $Cl$ is part of a double bond. It has $3$ sigma bonds,so it is $sp^2$ hybridized.
$C$. $CH_2=CH-CH_2-Cl$: The carbon attached to $Cl$ is bonded to one $C$ and two $H$ atoms (single bonds). It has $4$ sigma bonds,so it is $sp^3$ hybridized.
$D$. Chlorobenzene: The carbon attached to $Cl$ is part of the aromatic ring (double bond). It has $3$ sigma bonds,so it is $sp^2$ hybridized.
Therefore,the correct matching is: $(A-iii, B-ii, C-iii, D-ii)$.

(B-(II, IV), C-(I, III), D-(II, IV)) The classification of dihalides is as follows:
$1$. Geminal dihalides (or alkylidene halides) have two halogen atoms on the same carbon atom.
$2$. Vicinal dihalides (or alkylene dihalides) have two halogen atoms on adjacent carbon atoms.
Matching:
$A$. $H_3C-CH_2Cl$ is a mono-haloalkane (not a dihalide).
$B$. $ClCH_2-CH_2Cl$ has two $Cl$ atoms on adjacent carbons,so it is a vicinal dihalide $(ii)$ and an alkylene dihalide $(iv)$.
$C$. $C_6H_5-CHCl_2$ has two $Cl$ atoms on the same carbon,so it is a geminal dihalide $(i)$ and an alkylidene halide $(iii)$.
$D$. $C_6H_5-CHCl-CH_2Cl$ has two $Cl$ atoms on adjacent carbons,so it is a vicinal dihalide $(ii)$ and an alkylene dihalide $(iv)$.

(A) $(A) \rightarrow (iv, q)$: $CH_3CH_2CH_2Cl$ is $n$-propyl chloride ($IUPAC$: $1$-chloropropane).
$(B) \rightarrow (ii, p)$: $CH_3CHClCH_3$ is isopropyl chloride ($IUPAC$: $2$-chloropropane).
$(C) \rightarrow (iii, s)$: $CH_3CH(CH_3)CH_2Cl$ is isobutyl chloride ($IUPAC$: $1$-chloro-$2$-methylpropane).
$(D) \rightarrow (i, r)$: $(CH_3)_3CCH_2Cl$ is neopentyl chloride ($IUPAC$: $1$-chloro-$2,2$-dimethylpropane).

(A) The matching is as follows:
$A$ ($o$-Chlorotoluene) matches with $iv$ ($o$-Chlorotoluene) and $q$ ($2$-Chlorotoluene).
$B$ (Benzyl chloride) matches with $ii$ (Benzyl chloride) and $p$ (Chlorophenylmethane).
$C$ $(CH_3CH_2CHClCH_3)$ matches with $iii$ (sec-Butyl chloride) and $s$ ($2$-Chlorobutane).
$D$ $(CHBr_3)$ matches with $i$ (Bromoform) and $r$ (Tribromomethane).
Therefore,the correct matching is: $(A$ $\rightarrow iv, q), (B$ $\rightarrow ii, p), (C$ $\rightarrow iii, s), (D$ $\rightarrow i, r)$.

(A) The correct matches are:
$A \rightarrow i, r$
$B \rightarrow ii, s$
$C \rightarrow iv, q$
$D \rightarrow iii, p$

(N/A) The general scheme for $IUPAC$ nomenclature is: $2^{\circ} \text{ prefix} - 1^{\circ} \text{ prefix} - \text{Rootword} - 1^{\circ} \text{ suffix} - 2^{\circ} \text{ suffix}$.
For halo-substituted hydrocarbons:
$1$. $\text{Rootword} \Rightarrow$ Based on the total number of carbon atoms in the parent chain (e.g.,$Meth-, Eth-, Prop-, etc.$).
$2$. $1^{\circ} \text{ Prefix} \Rightarrow$ $Cyclo-$ (for aliphatic cyclic compounds).
$3$. $2^{\circ} \text{ Prefix} \Rightarrow$ $Halo-$ (e.g.,$Fluoro-, Chloro-, Bromo-, Iodo-$) and alkyl groups.
$4$. $1^{\circ} \text{ Suffix} \Rightarrow$ Indicates saturation or unsaturation:
$-ane$ (for $C-C$ single bonds)
$-ene$ (for $C=C$ double bonds)
$-yne$ (for $C \equiv C$ triple bonds)
$5$. $2^{\circ} \text{ Suffix} \Rightarrow$ Suffix of the most senior functional group (not applicable in simple alkyl halides).

Halogen atoms are more electronegative than carbon; therefore,the carbon-halogen bond of an alkyl halide is polarized. The carbon atom bears a partial positive charge $(\delta+)$ whereas the halogen atom bears a partial negative charge $(\delta-)$. The bond is represented as $C^{\delta+}-X^{\delta-}$.
As we go down the group in the periodic table,the size of the halogen atom increases. The fluorine atom is the smallest and the iodine atom is the largest. Consequently,the carbon-halogen bond length increases from $C-F$ to $C-I$.
Carbon-Halogen $(C-X)$ Bond Lengths,Bond Enthalpies,and Dipole Moments:

Bond	Bond length $/ pm$	$C-X$ Bond enthalpies $/ (kJ \ mol^{-1})$	Dipole moment $/$ Debye
$CH_3F$	$139$	$452$	$1.847$
$CH_3Cl$	$178$	$351$	$1.860$
$CH_3Br$	$193$	$293$	$1.830$
$CH_3I$	$214$	$234$	$1.636$

Order of dipole moment: $CH_3Cl$ > $CH_3F$ > $CH_3Br$ > $CH_3I$
Order of bond enthalpies: $CH_3F$ > $CH_3Cl$ > $CH_3Br$ > $CH_3I$

(D) Ethylidene chloride is a geminal dihalide where two chlorine atoms are attached to the same carbon atom.
Its chemical structure is $CH_3CHCl_2$.
The $IUPAC$ name for $CH_3CHCl_2$ is $1,1-$Dichloroethane.

(D) The given structure is $C_6H_5-CH=CH-CH(X)-CH_2-CH_3$.
In this compound,the halogen atom $(X)$ is attached to an $sp^3$ hybridized carbon atom,which is adjacent to a carbon-carbon double bond $(C=C)$.
Such compounds,where the halogen is attached to an $sp^3$ hybridized carbon next to a double bond,are classified as allylic halides.
Therefore,the correct option is $D$.

(A) vinylic halide is a compound in which the halogen atom is directly attached to a carbon atom that is part of a carbon-carbon double bond $(C=C)$.
In the structure provided in option $A$,the halogen $X$ is attached to a carbon atom that is $sp^2$ hybridized and part of a double bond,which defines it as a vinylic halide.
Option $B$ represents an allylic halide.
Option $C$ represents an aryl halide.
Option $D$ represents an allylic halide.

(A) Assertion $(A)$: The structure $CH_2=CH-CH_2-Cl$ contains a halogen atom attached to a carbon atom that is adjacent to a $C=C$ double bond. This is the definition of an allyl halide. Thus,Assertion $(A)$ is true.
Reason $(R)$: Allyl halides are defined as compounds where the halogen atom is attached to an $sp^3$ hybridized carbon atom,which is further bonded to a $C=C$ double bond. The statement provided in the original question incorrectly stated that the halogen is attached to an $sp^2$ carbon. Therefore,Reason $(R)$ is false.
Conclusion: $(A)$ is true but $(R)$ is false.

(A) vinylic halide is a compound in which the halogen atom is directly attached to a carbon atom that is part of a carbon-carbon double bond $(C=C-X)$.
In $1-$chloroethene $(CH_2=CHCl)$,the chlorine atom is attached to a carbon atom involved in a double bond,which satisfies the definition of a vinylic halide.
Therefore,the correct option is $A$.

(B) tertiary $(3^{\circ})$ alkyl halide is one in which the halogen atom is attached to a carbon atom that is further bonded to three other carbon atoms.
In option $B$,$(CH_3)_3C-Br$,the carbon atom bonded to the bromine atom is attached to three methyl groups,making it a tertiary carbon.
Thus,$(CH_3)_3C-Br$ is a tertiary alkyl halide.

(B) $1-$chloroethene $(CH_2=CHCl)$ is a vinylic halide because the halogen atom is attached to a carbon atom that is part of a carbon-carbon double bond. $\newline$ An allylic halide has the halogen atom attached to a carbon atom next to a carbon-carbon double bond. $\newline$ Therefore,the example $1-$chloroethene for an allylic halide is incorrect.

(B) The structure of allyl chloride is $CH_{2}=CH-CH_{2}Cl$.
Counting the atoms in the structure:
There are $3$ carbon atoms $(C_{3})$.
There are $5$ hydrogen atoms $(H_{5})$.
There is $1$ chlorine atom $(Cl)$.
Therefore,the molecular formula is $C_{3}H_{5}Cl$.

(A) Neohexyl chloride is the common name for $3,3-$dimethylbutyl chloride,which has the structure $(CH_{3})_{3}C-CH_{2}-CH_{2}-Cl$.
Option $A$ represents $3,3-$dimethylbutyl chloride (neohexyl chloride).
Option $B$ represents $n-$hexyl chloride.
Option $C$ represents $5-$methylhexyl chloride.
Option $D$ represents $3,3-$dimethyl$-2-$chlorobutane.

(A) The structure of $1-$chloro$-2,2-$dimethylpropane is $(CH_3)_3C-CH_2Cl$.
In this molecule,the carbon atom attached to the chlorine is a primary carbon,which is bonded to a quaternary carbon atom (a carbon bonded to four other carbons).
This structural arrangement,where a central carbon is bonded to three methyl groups and one $-CH_2Cl$ group,is commonly referred to as the $neo-$pentyl group.
Therefore,the common name for this compound is $neo-$pentyl chloride.

(D) An allylic halide is a compound in which the halogen atom is attached to an $sp^3$ hybridized carbon atom next to a carbon-carbon double bond $(C=C-C-X)$.
In option $A$,$B$,and $C$,the halogen atom $(X)$ is attached to the carbon atom directly adjacent to the double bond.
In option $D$,the structure is $CH_3-CH=CH-CH_2-CH_2-X$. Here,the halogen atom is attached to a carbon atom that is two positions away from the double bond,making it a homoallylic halide,not an allylic halide.
Therefore,the correct option is $D$.

(C) In allylic halides,the halogen atom is bonded to an $sp^3$ hybridized carbon atom that is directly attached to a carbon-carbon double bond.
The general structure is $CH_2=CH-CH_2-X$.
Therefore,$CH_2=CH-CH_2-X$ is an allylic halide.

(C) The general representation of a Grignard reagent is $R-Mg-X$,where $R$ is an alkyl or aryl group and $X$ is a halogen atom (such as $Cl$,$Br$,or $I$).

(B) In vinylic halides,the halogen atom is directly bonded to an $sp^2$ hybridized carbon atom of a carbon-carbon double bond.
In $CH_3-CH=CH-X$,the halogen atom $X$ is attached to the $sp^2$ hybridized carbon atom involved in the double bond,which satisfies the definition of a vinylic halide.

(D) benzylic halide is a compound in which the halogen atom is bonded to an $sp^3$ hybridized carbon atom that is directly attached to an aromatic ring.
In $4-$Iodotoluene,the iodine is attached directly to the benzene ring (aryl halide).
In $1-$Iodo$-2-$phenylethane,the iodine is attached to a carbon atom that is separated from the ring by another $CH_2$ group.
In Iodobenzene,the iodine is attached directly to the benzene ring (aryl halide).
In Iodophenylmethane (also known as benzyl iodide),the iodine is attached to a $CH_2$ group which is directly attached to the benzene ring. Thus,it is a benzylic halide.

(B) benzylic halide is a compound in which the halogen atom is bonded to an $sp^3$ hybridized carbon atom that is directly attached to an aromatic ring (benzene ring).
In $1-$chloro$-2-$phenylbutane $(CH_3-CH_2-CH(C_6H_5)-CH_2Cl)$,the chlorine atom is attached to a carbon atom that is not directly bonded to the benzene ring.
Therefore,it is not a benzylic halide.

(C) haloalkyne is an organic compound where a halogen atom is directly bonded to an $sp$ hybridized carbon atom of an alkyne group.
Example: $CH \equiv C-Cl$ (chloroethyne).
In this structure,the carbon atom bonded to the chlorine is $sp$ hybridized.

(C) An allylic halide is a compound in which the halogen atom is bonded to an $sp^3$ hybridized carbon atom next to a carbon-carbon double bond $(C=C-C-X)$.
In $3$-chloropropene $(CH_2=CH-CH_2Cl)$,the chlorine atom is attached to the $sp^3$ hybridized carbon atom which is adjacent to the $C=C$ double bond.
Therefore,$3$-chloropropene is an allylic halide.

(D) vinylic halide is defined as a compound in which the halogen atom is directly bonded to a carbon atom that is part of a carbon-carbon double bond $(C=C)$.
This carbon atom is $sp^2$ hybridized.
For example,in vinyl chloride $(CH_2=CHCl)$,the chlorine atom is attached to an $sp^2$ hybridized carbon atom of an aliphatic chain.

(C) The molecular formula $C_4H_9X$ corresponds to the alkyl group derived from butane $(C_4H_{10})$.
There are two isomeric alkanes with the formula $C_4H_{10}$: $n$-butane $(CH_3-CH_2-CH_2-CH_3)$ and isobutane $(CH_3-CH(CH_3)-CH_3)$.
For $n$-butane,there are two non-equivalent sets of hydrogen atoms,leading to two isomers: $1$-halobutane and $2$-halobutane.
For isobutane,there are two non-equivalent sets of hydrogen atoms,leading to two isomers: $1$-halo-$2$-methylpropane and $2$-halo-$2$-methylpropane.
Thus,the total number of possible monohalogen derivatives is $2 + 2 = 4$.

(C) An allylic halide is a compound in which the halogen atom is bonded to an $sp^3$ hybridized carbon atom next to a carbon-carbon double bond $(C=C)$.
In $3-$bromopropene $(CH_2=CH-CH_2Br)$,the bromine atom is attached to a carbon atom that is adjacent to the double bond,which satisfies the definition of an allylic halide.
$1-$Bromopropene and $2-$bromopropene are vinylic halides because the halogen is attached directly to the double-bonded carbon atom.

(D) benzylic halide is a compound in which the halogen atom is bonded to a carbon atom that is directly attached to an aromatic ring (specifically,a $sp^3$ hybridized carbon atom adjacent to the benzene ring).
$1.$ Bromophenylmethane $(C_6H_5CH_2Br)$ is a benzylic halide.
$2.$ $1-$Bromo$-1-$phenylpropane $(C_6H_5CH(Br)CH_2CH_3)$ is a benzylic halide.
$3.$ $2-$Bromo$-2-$phenylpropane $(C_6H_5C(Br)(CH_3)_2)$ is a benzylic halide.
$4.$ $1-$Bromo$-2-$phenylbutane $(C_6H_5CH_2CH(Br)CH_2CH_3)$ has the bromine atom attached to a carbon that is not directly bonded to the benzene ring. The carbon attached to the benzene ring is a $CH_2$ group,and the bromine is on the second carbon of the alkyl chain. Therefore,it is not a benzylic halide.

(D) An allylic halide is a compound in which the halogen atom is bonded to an $sp^3$ hybridized carbon atom that is adjacent to a carbon-carbon double bond $(C=C-C-X)$.
In option $A$,$CH_2=CH-CH_2-X$,the halogen is attached to an allylic carbon.
In option $B$,$CH_3-CH=CH-CH_2-X$,the halogen is attached to an allylic carbon.
In option $C$,$CH_3-CH_2-CH=CH-CH_2-X$,the halogen is attached to an allylic carbon.
In option $D$,$CH_3-CH=CH-CH_2-CH_2-X$,the halogen is attached to a carbon atom that is two positions away from the double bond,making it a homoallylic halide,not an allylic halide.

(A) haloalkyne is a compound in which a halogen atom is directly attached to a carbon atom that is part of a carbon-carbon triple bond $(C \equiv C)$.
In a carbon-carbon triple bond,the carbon atom is $sp$ hybridized.
Therefore,the halogen atom is bonded to an $sp$ hybridized carbon atom.

(B) haloalkyne is an organic compound that contains both a halogen atom $(X)$ and a carbon-carbon triple bond $(C \equiv C)$.
- Option $(A)$ $CH_3-CH_2-CH=CH-X$ is a haloalkene because it contains a double bond $(C=C)$.
- Option $(B)$ $CH_3-C \equiv C-CH_2-X$ is a haloalkyne as it contains a triple bond $(C \equiv C)$ and a halogen atom $(X)$.
- Option $(C)$ $CH \equiv C-CH_2-CH_2-X$ is also a haloalkyne.
- Option $(D)$ $CH_3-CH_2-C \equiv C-X$ is also a haloalkyne.
Given the standard nomenclature and structure,options $(B)$,$(C)$,and $(D)$ all represent haloalkynes. However,in many textbook contexts,the simplest representation or specific structural isomer is sought. Since multiple options are technically correct,we identify the structure containing the functional group as requested.

(C) In vinylic halides,the halogen atom is bonded to a $sp^{2}$ hybridized carbon atom of an aliphatic chain.
Since a vinylic halide contains a carbon-carbon double bond,it is classified as a haloalkene.

(A) In a haloalkyne,the halogen atom is directly bonded to an $sp$ hybridized carbon atom of the triple bond.
In $Chloroethyne$ $(CH \equiv C-Cl)$,the chlorine atom is attached to the $sp$ hybridized carbon atom.
In the other options,the chlorine atom is attached to $sp^3$ hybridized carbon atoms.
Therefore,chloroethyne is a haloalkyne.