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4.6.1Unit 4. Rates, Equilibria and Further Organic Chemistry

Chirality in Optical Isomers — IAL Edexcel Linear (Chemistry) Revision Notes & Topical Questions

5 min read 4 parts Lesson 42 of 56 Unit quiz

📚 IAL Edexcel Linear (Chemistry) Hub / Topical Revision
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Curriculum Equation Key معادلة تفاعل تكوين الإستر (الأسترة) - Esterification Reaction EquationFast Exam Solution
R-COOH + R2-OH ⇌ (conc. H₂SO₄) R-COO-R2 + H₂O
Word Equation & Conditions: حمض كربوكسيلي + كحول (في وجود حمض الكبريتيك المركز كعامل حفاز ونازع للماء) ⇌ إستر + ماء
Location & Specifications: الكيمياء العضوية للثانوية العامة والتحصيلي و Edexcel Chemistry.
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Part 1 of 3Chiral Centres

Optical isomerism is a type of stereoisomerism found in molecules that lack a plane of symmetry.

Chiral carbon
  • Chiral carbon A carbon atom bonded to four different atoms or groups is called a chiral centre or asymmetric carbon.
Examples
  • Examples Butan-2-ol, 2-bromobutane and 2-hydroxypropanoic acid each contain one carbon with four different groups attached.
Not chiral
  • Not chiral Propan-2-ol is not chiral because the central carbon carries two identical methyl groups.
Marking
  • Marking Chiral centres are often marked with an asterisk on the structural formula to help identify them.

Part 2 of 3Enantiomers

A chiral molecule exists as two forms called enantiomers.

Enantiomers
Mirror images
  • Mirror images Enantiomers are non-superimposable mirror images, like a left and right hand, and cannot be rotated into each other.
3D drawing
  • 3D drawing Draw the chiral carbon with two bonds in the plane, one wedge toward the viewer and one dashed away.
Same properties
  • Same properties Enantiomers have the same boiling point, melting point and chemical reactions with non-chiral reagents.
Biological difference
  • Biological difference They can behave differently in living systems because enzymes and receptors are themselves chiral.

Part 3 of 3Exam Checklist & Tips

4.6.1 – Key Points for the Exam

  • Chiral centre Carbon atom attached to four different groups.
  • Enantiomers Non-superimposable mirror image stereoisomers.
  • Plane-polarised light Light that vibrates in only one plane.
  • Optical activity The ability to rotate the plane of polarised light.

Common Mistakes

  • Calling a carbon chiral when two of its four groups are the same.
  • Saying enantiomers have different melting points.
  • Drawing the mirror image as a simple rotation of the original molecule.
  • Thinking all molecules containing a chiral carbon cannot be separated into optical forms.

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