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The incorrect statements regarding geometrical isomerism are : (A) Propene shows geometrical isomerism. (B) Trans isomer has identical atoms/groups on the opposite sides of the double bond. (C) Cis-but-2-ene has higher dipole moment than trans-but-2-ene. (D) 2-methylbut-2-ene shows two geometrical isomers. (E) Trans-isomer has lower melting point that cis isomer. Choose the CORRECT answer from the options given below : (1) (A), (D) and (E) only (2) (C), (D) and (E) only (3) (B) and (C) only (4) (A) and (E) only

### Step-by-Step Verification 1. **Check Propene (CH₃–CH=CH₂)** • Right-hand carbon has two H’s ⇒ only one unique group • No geometrical isomerism ⇒ Statement (A) is **wrong** 2. **Definition of Trans** • Trans = identical groups on opposite sides ⇒ Statement (B) is **correct** 3. **Dipole in But-2-ene** • In cis-isomer, CH₃ vectors reinforce • In trans-isomer, CH₃ vectors cancel • $ herefore$ $\mu_{cis} > \mu_{trans}$ ⇒ Statement (C) is **correct** 4. **2-Methylbut-2-ene (CH₃–C(CH₃)=CH–CH₃)** • Left carbon attached to CH₃ & CH₃ (identical) • Cannot form cis/trans ⇒ Statement (D) is **wrong** 5. **Melting Points** • Trans isomers more symmetrical → better crystal packing → **higher** $T_m$ than cis • Statement (E) says the opposite ⇒ **wrong** ### List of Incorrect Statements (A), (D), (E) ### Final Answer **Option (1)**

The incorrect statements regarding geometrical isomeris... - Solution & Explanation | iExplain

Detailed Explanation

Key Theory

Requirement for Geometrical (cis–trans) Isomerism
• Each carbon of the C=C must be bonded to two different substituents.
• If either carbon carries two identical groups, no cis/trans is possible.
Cis vs. Trans
• Cis: Identical (or priority-1) groups on the same side of the double bond.
• Trans: Identical (or priority-1) groups on opposite sides.
Physical Property Trends
• Melting point: Trans > Cis (better crystal packing).
• Boiling point & Dipole: Cis > Trans (net dipole higher in cis).

Applying the Theory to Each Statement

Label	Molecule / Statement	Why it is Correct or Wrong
(A)	Propene has CH₃–CH=CH₂	Terminal carbon has two H’s → no geometrical isomerism → statement wrong
(B)	Definition of trans	Matches textbook definition → statement right
(C)	Dipole of cis-but-2-ene higher	True, vectors add → statement right
(D)	2-Methylbut-2-ene gives two GI	Left C of C=C has two CH₃’s (identical) → no GI → statement wrong
(E)	Trans melts lower than cis	Trend is opposite → statement wrong

Hence the incorrect ones are (A), (D), (E).

Simple Explanation (ELI5)

What’s Being Asked?

Imagine you have toy cars linked by a stiff rod (the double bond). Because the rod can’t twist, the cars may be stuck facing the same direction (cis) or opposite directions (trans).
The question lists five sentences about these “stuck-together” cars and asks which sentences are wrong.

How To Check Each Sentence

Propene: One end of the rod has two identical wheels (two H’s), so you can’t tell left from right—no cis/trans possible.
Trans meaning: "Same pieces on opposite sides" is the right definition.
Dipole moment: When the big pieces (CH₃) sit on the same side (cis), their little pulls add up, so the magnet‐arrow (dipole) is bigger than in trans.
2-Methylbut-2-ene: One end of the rod again has two identical CH₃ groups, so it can’t have cis/trans.
Melting point: Trans shapes are straighter like sticks and pack better, so they usually melt at higher temperatures than the bent cis shapes.

Result

So the wrong ones are (A), (D), and (E).

Step-by-Step Solution

Step-by-Step Verification

Check Propene (CH₃–CH=CH₂)
• Right-hand carbon has two H’s ⇒ only one unique group
• No geometrical isomerism ⇒ Statement (A) is wrong
Definition of Trans
• Trans = identical groups on opposite sides ⇒ Statement (B) is correct
Dipole in But-2-ene
• In cis-isomer, CH₃ vectors reinforce
• In trans-isomer, CH₃ vectors cancel
• $herefore$ $\mu_{cis} > \mu_{trans}$ ⇒ Statement (C) is correct
2-Methylbut-2-ene (CH₃–C(CH₃)=CH–CH₃)
• Left carbon attached to CH₃ & CH₃ (identical)
• Cannot form cis/trans ⇒ Statement (D) is wrong
Melting Points
• Trans isomers more symmetrical → better crystal packing → higher $T_m$ than cis
• Statement (E) says the opposite ⇒ wrong

List of Incorrect Statements

(A), (D), (E)

Final Answer

Option (1)

Examples

Example 1

Cis and trans fats: trans fats pack tightly, giving them higher melting points—hence they are solid at room temperature, unlike cis vegetable oils.

Example 2

Vision chemistry: the cis–trans isomerisation of retinal in our eyes triggers the vision signal.

Example 3

Polymer stiffness: trans-polyisoprene (gutta-percha) is hard; cis-polyisoprene (natural rubber) is elastic—the difference is just cis vs. trans at many double bonds.

Visual Representation

References

[1]Paula Yurkanis Bruice – Organic Chemistry (chapter on stereochemistry)
[2]Peter Sykes – A Guidebook to Mechanism in Organic Chemistry (section on cis–trans isomerism)
[3]IIT JEE Main & Advanced – Previous Years’ Question Papers on Stereochemistry
[4]NCERT Chemistry Class 11 – Chapter 12 Organic Chemistry: Some Basic Principles and Techniques