chirality

chirality — adjective

  • chiralitypositive
  • more chiralitycomparative
  • most chiralitysuperlative

1. describes an individual molecule or object whose mirror-image counterpart cannot

1.adjectiveC1
Definition

describes an individual molecule or object whose mirror-image counterpart cannot be aligned with the original by any rotation — the geometric property of handedness, illustrated by a left hand and a right hand that are mirror images but cannot occupy the same glove.

Example

A chiral molecule, like the compound limonene, has left-handed and right-handed forms that smell completely different.

chiral + molecule; attributive use before noun

Niran checked whether the crystal was chiral by comparing it with its mirror image under the microscope.

predicative: is / was chiral

Common collocations
  • chiral molecule
  • chiral compound
  • chiral object
  • chiral structure
  • chiral substance
  • chiral catalyst
Synonyms
  • non-superimposable

    more literal and technical; describes the specific geometric relationship rather than a general class property

  • enantiomorphic

    rare; used mainly in crystallography to describe mirror-image crystal forms

Antonyms
  • achiral

    describes a molecule whose mirror image CAN be placed exactly on top of the original (e.g. methane, water)

Grammar Patterns

chiral + noun (molecule / compound / object / structure)

is / are chiral

Usage Note

Commonly used attributively before nouns like 'molecule', 'compound', 'substance', or 'catalyst'. The term comes from the Greek word for 'hand' — the hand is the classic example of a chiral object whose mirror image (the opposite hand) does not match the original.

Common Mistakes

The molecule is chiral because it is asymmetric.
The molecule is chiral because its mirror image cannot be placed on top of it to match exactly.
'asymmetric' is broader; chirality specifically refers to mirror-image non-superimposability.
This carbon atom is chiral.
This carbon atom is a chiral center (or asymmetric center).
Atoms themselves are not chiral; they are centers that cause chirality in the molecule.

2. identifying a chemical substance or system as belonging to the class of compound

2.adjectiveC1
Definition

identifying a chemical substance or system as belonging to the class of compounds that exist as two distinct mirror-image forms, used when discussing their classification, recognition, or separation rather than the geometric relationship itself.

Example

Glucose and other sugars are naturally chiral, and each mirror version rotates plane-polarised light in a different direction.

predicative use: be + chiral

The chiral nature of DNA determines how the molecule twists and fits inside the cell nucleus.

attributive: chiral + nature

Common collocations
  • chiral nature
  • chiral form
  • chiral version
  • chiral environment
  • chiral recognition
  • chiral separation
Synonyms
  • optically active

    a property-based synonym; chiral compounds rotate plane-polarised light, though not all chiral substances are optically active in all forms

Grammar Patterns

chiral + noun (nature / environment / interaction / separation / recognition)

be chiral in nature / form

Usage Note

This sense focuses on the classification of substances as belonging to the chiral class — it is the most general of the three senses. Unlike sense 1, which emphasises the structural relationship to a mirror image, this sense simply identifies substances or phenomena that have the property of chirality.

Common Mistakes

This reaction is chiral.
This reaction produces chiral molecules.
The reaction itself is not chiral; the products are.

3. describing a specific atom within a molecule — most often a carbon atom — that h

3.adjectiveC2
Definition

describing a specific atom within a molecule — most often a carbon atom — that has four different atoms or groups attached to it, making the whole molecule capable of existing as mirror-image forms.

Example

In alanine, the central carbon atom is called a chiral center because it bonds to four different groups.

attributive: chiral + center (most common collocation)

Soraya found three chiral carbon atoms in the plant compound by examining its structure with X-ray analysis.

attributive: chiral + carbon

Common collocations
  • chiral center
  • chiral carbon
  • chiral atom
  • chiral centre (British spelling)
Synonyms
  • asymmetric center

    the preferred term in many textbooks; 'asymmetric' is broader but in this context refers specifically to a tetrahedral atom with four different substituents

  • stereocenter

    broader term that includes but is not limited to chiral centers; any atom where swapping two groups gives a different stereoisomer

Grammar Patterns

chiral + noun (center / carbon / atom / molecule)

Usage Note

This sense is narrower than senses 1 and 2: it refers specifically to an atom (the source of chirality) rather than the whole molecule. The most common collocations are 'chiral center' and 'chiral carbon.' A molecule may have one, several, or no chiral centers. Frequently used in stereochemistry and pharmaceutical research writing.

Common Mistakes

This molecule has a chiral carbon.
This molecule contains a chiral carbon atom.
It is clearer to specify that the carbon has four different substituents, not that the carbon itself is chiral.

Word family

  • chiral
    adjectiveC1
  • achiral
    adjectiveC2
  • enantiomer
    nounC2
  • enantiomorphic
    adjectiveC2

Synonym discussion

Sense: adjective/1

'Chiral' specifically describes an object whose mirror image cannot be placed exactly on top of the original — like a left hand compared with a right hand. 'Asymmetric' is a much broader term that simply means 'not symmetrical' and applies to shapes, graphs, social patterns, and countless other contexts beyond mirror-image relationships. 'Non-superimposable' is a more literal and technical description of the same property as 'chiral,' but it is less common in general scientific writing because it is longer and more formal. 'Enantiomorphic' is a rarer synonym used mainly in crystallography to describe mirror-image crystal forms themselves. In everyday chemistry writing, 'chiral' is the standard term, while 'asymmetric' is preferred when referring specifically to the carbon atom ('asymmetric carbon') that creates chirality in a molecule.

chiralasymmetricnon-superimposableenantiomorphic

Common collocations

Nouns

  • chirality
  • enantiomer
  • isomer
  • stereochemistry
  • racemic mixture
  • optical activity

Adverbs

  • structurally chiral
  • inherently chiral
  • biologically chiral
  • optically chiral

Phrases

  • chiral recognition process
  • chiral separation technique
  • chiral resolution method

Prepositions

  • chiral in nature
  • chiral by design

Etymology

GreekEnglish

Coined by the Scottish physicist Lord Kelvin in 1894 from the Greek word 'cheir' (χείρ), meaning 'hand.' Kelvin used it to describe the property of an object whose mirror image cannot be rotated to match the original — exactly the relationship between a left hand and a right hand, which are mirror images but not identical.

First known use

1894

1894, in the meaning defined above