Geometrical Isomerism in Organic Compounds

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Questions and Answers

Which of the following describes compounds that contain double bonds?

  • They do not contain any carbon atoms.
  • They are always linear.
  • They are always symmetrical.
  • They can be unsymmetrical. (correct)

What is an example of a compound with double bonds based on the content?

  • C4H10
  • CH=CH2 (correct)
  • C2H6
  • C3H8

In the configuration of a compound with the formula C4H4, how many double bonds are indicated?

  • Three double bonds
  • No double bonds
  • One double bond
  • Two double bonds (correct)

Which chemical structure illustrates an unsymmetrical compound with double bonds?

<p>CH=CH-CH=CH2 (B)</p> Signup and view all the answers

Which of the following statements about geometrical compounds is true?

<p>They may exhibit different physical properties due to their structure. (A)</p> Signup and view all the answers

What determines whether a compound is classified as an isomer?

<p>The molecular structure and connectivity (D)</p> Signup and view all the answers

Which term refers to isomers that have the same molecular formula but different structural arrangements?

<p>Structural Isomers (B)</p> Signup and view all the answers

What is indicated by the term 'cis' in isomer nomenclature?

<p>Atoms are on the same side of a double bond (D)</p> Signup and view all the answers

What molecular configuration would a compound in a trans isomer have?

<p>Atoms are positioned on opposite sides of a structural backbone (A)</p> Signup and view all the answers

In the context of geometrical isomers, what distinguishes an 'odd' numbered compound?

<p>It has an asymmetric structure leading to unique properties (A)</p> Signup and view all the answers

Which statement about symmetrical isomers is true?

<p>They have identical chemical and physical properties (D)</p> Signup and view all the answers

How does a compound represented as Heya-2,4-diene exhibit isomerism?

<p>Through different positions of double bonds (D)</p> Signup and view all the answers

Which of the following compounds would NOT be considered an isomer?

<p>C2H6 with no alternative formation (D)</p> Signup and view all the answers

Which property is generally higher for trans isomers compared to cis isomers?

<p>Boiling points (D)</p> Signup and view all the answers

Which is true about the dipole moment of cis isomers?

<p>It is generally greater than that of trans isomers. (B)</p> Signup and view all the answers

What is a characteristic feature of trans isomers in terms of packing?

<p>They have a close-packed structure. (A)</p> Signup and view all the answers

Which of the following compounds is least likely to show geometric isomerism?

<p>1-butene (C)</p> Signup and view all the answers

Why do cis isomers typically have lower solubility than trans isomers?

<p>They have a more polar structure. (B)</p> Signup and view all the answers

How do the molecular structures of cis and trans isomers differ?

<p>Cis isomers have adjacent similar groups while trans has opposite sides. (D)</p> Signup and view all the answers

How many geometric isomers are possible for hexachloro cyclohexane?

<p>2 (B)</p> Signup and view all the answers

Which of the following statements about geometric isomers is true?

<p>Cis isomers experience steric strain more than trans isomers. (C)</p> Signup and view all the answers

What structural feature differentiates the cis and trans isomers of decalin?

<p>Position of the cyclohexane rings (C)</p> Signup and view all the answers

In terms of boiling points, how do cis and trans isomers typically compare?

<p>Cis isomers usually have higher boiling points due to higher polarity. (C)</p> Signup and view all the answers

Which of these describes a characteristic of geometric isomers?

<p>They have the same molecular formula. (B)</p> Signup and view all the answers

Which of the following compounds are considered geometric isomers?

<p>cis-2-butene and trans-2-butene (D)</p> Signup and view all the answers

In the context of chemical compounds, what does the term 'bicyclo' refer to?

<p>Compounds with two fused rings (B)</p> Signup and view all the answers

Which molecule would likely exhibit cis trans isomerism?

<p>Cis- and trans-2-butene (A)</p> Signup and view all the answers

What is a common feature of geometric isomers that affects their physical properties?

<p>Differences in boiling and melting points (B)</p> Signup and view all the answers

Which statement is true regarding the stability of cis and trans isomers?

<p>Trans isomers are typically more stable due to steric hindrance. (D)</p> Signup and view all the answers

Which type of geometric isomers is described in the content?

<p>Cis and trans isomers (B)</p> Signup and view all the answers

What hybridization is indicated for the structure discussed in the content?

<p>sp³d (D)</p> Signup and view all the answers

Which molecular arrangement applies to the isomers discussed specifically in the context given?

<p>Opposite groups (D)</p> Signup and view all the answers

Which chemical formula represents a methyl derivative mentioned in the content?

<p>C₇H₈ (D)</p> Signup and view all the answers

How is the geometrical relationship characterized in the context?

<p>Based on the position of substituents (C)</p> Signup and view all the answers

Flashcards

Geometric Isomers

Compounds where the atoms within the molecule are arranged in a particular spatial configuration.

Double Bonds

Presence of at least one double bond within a molecule.

Consistutionally Unsymmetrical

Condition where the molecule has a mirror image that is not superimposable on the original molecule.

Geometric Isomers due to Double Bonds

Different arrangements of atoms around a double bond, leading to distinct compounds.

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Cis Isomers

Geometric isomers that have the same groups on the same side of the double bond.

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Chiral Molecule

A molecule that has a mirror image that cannot be superimposed on the original molecule.

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Trans Isomer

Geometric isomers that have the same groups on opposite sides of the double bond.

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Isomer

A chemical compound with the same molecular formula but different structural arrangements of atoms, which leads to different properties.

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Carbon Chain Length

The number of carbon atoms in the main chain of the molecule.

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Single Bond

A molecule with a single bond.

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Condition for Geometric Isomerism

A molecule with a double bond can exhibit geometric isomerism only if the two carbon atoms involved in the double bond are each attached to two different groups.

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Dipole Moment in Geometric Isomers

Cis isomers have a greater dipole moment compared to trans isomers due to the alignment of their bond dipoles.

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Boiling Points of Geometric Isomers

Cis isomers generally have higher boiling points compared to trans isomers due to their stronger intermolecular forces.

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Melting Points of Geometric Isomers

Trans isomers generally have higher melting points compared to cis isomers due to their more compact and efficient packing in the solid state.

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Solubility of Geometric Isomers

Cis isomers generally exhibit lower solubility compared to trans isomers due to their higher polarity.

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Chiral

A molecule that cannot be superimposed on its mirror image.

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Locked Isomers

A pair of geometric isomers that cannot interconvert by rotation around a single bond due to the presence of a ring or a double bond.

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Hexachlorocyclohexane

The molecule with one chlorine atom on each carbon atom in the cyclohexane ring, resulting in eight possible geometric isomers.

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Decalin

A bicyclic molecule with two fused cyclohexane rings. It exists in cis and trans forms.

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Constitutional Isomers

A type of isomer where the atoms are connected in a different order, resulting in different functional groups.

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Octahedral Complex

The central atom with six surrounding atoms is called the 'octahedral complex'. It has a specific orientation for all six surrounding atoms.

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Hybridisation of Octahedral Complex

The hybridisation of the central atom in an octahedral complex involves mixing one 's' atomic orbital, three 'p' atomic orbitals and two 'd' atomic orbitals. This creates six equivalent hybrid orbitals.

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Study Notes

Geometrical Isomerism in Compounds

  • Compounds containing more than one double bond (alternate double bonds) can exhibit geometric isomerism.
  • If a compound is constitutionally unsymmetrical, the total number of geometric isomers is 2n, where n is the number of double bonds.
  • Example: Hepta-2,4-diene (H2C=CH-CH=CH-CH2-CH3) has 22 =4 isomers.

Case II: Constitutionally Symmetrical Compounds

  • If a compound is constitutionally symmetrical, the number of geometric isomers depends on whether 'n' (the number of double bonds) is even or odd.
    • If 'n' is even, the number of geometric isomers = 2n-1/2 + 2n-1/2 = 2n-1 + 2n-1
    • If 'n' is odd, the number of geometric isomers = 2n-1/2 + 2n-1/2 = 2n-1.
  • Example: Hexa-2,4-diene (H2C=CH-CH=CH-CH=CH2) with n=3, has 23-1 = 4 geometric isomers.

Properties of Geometric Isomers (cis-trans isomers)

  • Dipole moment: Generally, cis-isomers have a greater dipole moment than trans-isomers. Hence, cis-isomers are more polar than trans-isomers.
  • Boiling points: Cis isomers generally have higher boiling points than trans isomers due to their more polar nature.
  • Melting points: Trans isomers generally have higher melting points than cis isomers because of their more compact structure, which allows for closer packing.
  • Solubility: Trans isomers have lower solubility than cis isomers.

Compounds that do not show Geometrical Isomerism

  • Compounds that have identical groups on each side of the double bond will not exhibit geometric isomerism.

Calculating Possible Geometrical Isomers for 1,2,3,4,5,6-Hexachloro Cyclohexane

  • There are 8 possible geometrical isomers.

How Many Geometrical Isomers for Specific Compounds?

  • Decalin: 2 isomers
  • 1-Methyl decalin: 4 isomers
  • 9-Methyl decalin: 2 isomers

Geometrical Isomers in SF2Cl2Br2

  • There are 5 possible geometrical isomers for the compound. The shape is octahedral.

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