Editing Tacticity (section)

{{Short description|Relative conformational uniformity of repeating units in a macromolecule}}
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[[Image:Syndiotactic polypropene.png|thumb|right|A ball-and-stick model of syndiotactic [[polypropylene]].]]
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'''Tacticity''' (from {{langx|el|τακτικός|taktikos}}, "relating to arrangement or order") is the relative [[stereochemistry]] of adjacent [[chirality (chemistry)|chiral]] centers within a [[macromolecule]].<ref>''Introduction to polymers'' R.J. Young {{ISBN|0-412-22170-5}}{{page needed|date = December 2024}}{{full|date = December 2024}}</ref>{{better source|date = December 2024}} The practical significance of tacticity rests on the effects on the physical properties of the [[polymer]].{{citation needed lead|date = December 2024}} The regularity of the macromolecular structure influences the degree to which it has rigid, [[Crystallinity|crystalline]] long range order or flexible, [[amorphous]] long range disorder.{{citation needed lead|date = December 2024}} Precise knowledge of tacticity of a polymer also helps understanding at what temperature a polymer [[melting|melts]], how [[soluble]] it is in a [[solvent]],{{citation needed lead|date = December 2024}} as well as its mechanical properties.{{citation needed lead|date = December 2024}}

A '''tactic macromolecule''' in the [[IUPAC]] definition is a macromolecule in which essentially all the configurational (repeating) units are identical. In a hydrocarbon macromolecule with all carbon atoms making up the backbone in a [[tetrahedral molecular geometry]], the zigzag backbone is in the paper plane with the substituents either sticking out of the paper or retreating into the paper;{{Overly detailed inline|date = December 2024}}, this projection is called the [[Natta projection|Natta projection after Giulio]] [[Giulio Natta|Natta]].{{citation needed lead|date = December 2024}} Tacticity is particularly significant in [[vinyl polymer]]s of the type -{{chem|H|2|C-CH(R)-}}, where each [[repeating unit]] contains a [[substituent]] R attached to one side of the polymer [[Backbone chain|backbone]]. The arrangement of these substituents can follow a regular pattern- appearing on the same side as the previous one, on the opposite side, or in a random configuration relative to the preceding unit. '''Monotactic''' macromolecules have one [[Stereoisomerism|stereoisomeric]] atom per repeat unit,{{citation needed lead|date = December 2024}} '''ditactic''' to '''n-tactic''' macromolecules have more than one stereoisomeric atom per unit.{{citation needed lead|date = December 2024}}

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 |title =[[International Union of Pure and Applied Chemistry|IUPAC]] definition
 |quote = The orderliness of the succession of configurational repeating units in<br/>the main chain of a regular [[macromolecule]], a regular oligomer molecule,<br/>a regular block, or a regular chain.<ref>{{cite journal |title=Glossary of basic terms in polymer science (IUPAC Recommendations 1996) |journal=[[Pure and Applied Chemistry]] |year=1996 |volume=68 |issue=12 |pages=2287–2311 |doi=10.1351/pac199668122287 |url=http://pac.iupac.org/publications/pac/pdf/1996/pdf/6812x2287.pdf |last1=Jenkins |first1=A. D. |last2=Kratochvíl |first2=P. |last3=Stepto |first3=R. F. T. |last4=Suter |first4=U. W. |s2cid=98774337 |access-date=2013-07-25 |archive-date=2016-03-04 |archive-url=https://web.archive.org/web/20160304041907/http://pac.iupac.org/publications/pac/pdf/1996/pdf/6812x2287.pdf |url-status=dead }}</ref> 
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