The IUPAC name of ethylidene chloride is:

Step 1: Understand common names

Ethylidene chloride is a common name for a geminal dihalide (both halogens on the same carbon).

The suffix "-ylidene" indicates that both halogen atoms are attached to the same carbon.

Step 2: Determine the structure

Ethylidene chloride has:

• 2 carbons ("eth-")
• 2 chlorine atoms on the same carbon ("ylidene")

Structure: $\ce{CH3-CHCl2}$

Step 3: Apply IUPAC nomenclature

IUPAC naming:

1. Parent chain: 2 carbons = ethane
2. Two chlorine atoms at position 1: 1,1-dichloro
3. Full name: 1,1-Dichloroethane

Step 4: Verify other options

• (a) 1-Chloroethene: $\ce{CH2=CHCl}$ - only one Cl, has a double bond
• (b) 1-Chloroethyne: $\ce{HC≡CCl}$ - only one Cl, has a triple bond
• (c) 1,2-Dichloroethane: $\ce{CH2Cl-CH2Cl}$ - two Cl on different carbons (ethylene dichloride)
• (d) 1,1-Dichloroethane: $\ce{CH3-CHCl2}$ - two Cl on the same carbon ✓

Answer: (d)

Key Points:

• Ethylidene chloride (common) = 1,1-Dichloroethane (IUPAC)
• Ethylene chloride (common) = 1,2-Dichloroethane (IUPAC)
• "-ylidene" suffix → geminal dihalide (both X on same C)
• "-ylene" suffix → vicinal dihalide (X on adjacent C)