Which of the following species is non- polar ?

Options

A. trans - pent - 2 - ene
B. cis - pent - 2 - ene
C. cis - 1 - chloropropene
D. `SF_6`

Answer

To determine which of the given species is non-polar, we will analyze each option step by step.

### Step 1: Analyze Trans-Pent-2-ene
- **Structure**: Trans-pent-2-ene has the following structure:
\[ CH_3 - CH = CH - CH_2 - CH_3 \]
- **Polarity**: In trans-pent-2-ene, the bulky groups (CH3) are on opposite sides of the double bond. This symmetry allows the dipole moments to cancel out, resulting in a net dipole moment that is not equal to zero. Thus, trans-pent-2-ene is a polar molecule.

### Step 2: Analyze Cis-Pent-2-ene
- **Structure**: Cis-pent-2-ene has the following structure:
\[ CH_3 - CH = CH - CH_2 - CH_3 \]
- **Polarity**: In cis-pent-2-ene, the bulky groups (CH3) are on the same side of the double bond. This arrangement does not allow the dipole moments to cancel out, leading to a net dipole moment that is not equal to zero. Therefore, cis-pent-2-ene is also a polar molecule.

### Step 3: Analyze Cis-1-Chloropropene
- **Structure**: Cis-1-chloropropene has the following structure:
\[ CH_3 - C(Cl) = CH_2 \]
- **Polarity**: In this molecule, the chlorine atom introduces a significant dipole moment due to its electronegativity. The arrangement is such that the dipole moments do not cancel out, resulting in a net dipole moment that is not equal to zero. Hence, cis-1-chloropropene is a polar molecule.

### Step 4: Analyze SF6
- **Structure**: SF6 has the following structure:
\[ \text{Octahedral structure with S in the center and F atoms at the vertices.} \]
- **Polarity**: In SF6, all six fluorine atoms are equivalent and symmetrically arranged around the sulfur atom. The dipole moments of the SF bonds cancel each other out due to this symmetry, resulting in a net dipole moment that is equal to zero. Therefore, SF6 is a non-polar molecule.

### Conclusion
Based on the analysis, the species that is non-polar is **SF6**.

### Final Answer:
**SF6 (Option D)**

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