From Wikipedia, the free encyclopedia
A polycarbonate is an oxocarbon dianion consisting of a chain of carbonate units, where the successive carbonyl groups are directly linked to each other by shared additional oxygen atoms. That is, they are the conjugate bases of polycarbonic acids , the conceptual anhydrides of carbonic acid or polymers of carbon dioxide . They have the structure – O[(C=O)–O]n – and molecular formula [Cn O2n +1 ]2– .
Whereas the carbonate dianion itself is well known, as found in many salts , many organic compounds containing esters of it have been made, and the parent carbonic acid is also well-known, higher homologs are substantially less stable. Only a few examples of covalent dicarbonate and tricarbonate structures and ionic dicarbonate salts have been made and their conjugate acids have only been studied theoretically. Polycarbonates up to n =6 have been studied theoretically, with the dianions being only metastable but stabilized when paired with metal counterions or as their conjugate acids.[1]
Di-tert -butyl tricarbonate extrudes carbon dioxide in the presence of various catalysts to form di-tert -butyl dicarbonate .[2] exothermically .[3]
Polycarbonates and their conjugate acids
Carbonate units
(Poly)carbonate
(Poly)carbonic acid
1
O
−
−
C
O
‖
−
O
−
{\displaystyle {\ce {^{-}O-{\overset {\displaystyle O \atop \|}{C}}-O^{-}}}}
Carbonate
HO
−
C
O
‖
−
OH
{\displaystyle {\ce {HO-{\overset {\displaystyle O \atop \|}{C}}-OH}}}
Carbonic acid
2
O
−
−
C
O
‖
−
O
−
C
O
‖
−
O
−
{\displaystyle {\ce {^{-}O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O^{-}}}}
Dicarbonate
HO
−
C
O
‖
−
O
−
C
O
‖
−
OH
{\displaystyle {\ce {HO-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-OH}}}
Dicarbonic acid
3
O
−
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
{\displaystyle {\ce {^{-}O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O^{-}}}}
Tricarbonate
HO
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
OH
{\displaystyle {\ce {HO-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-OH}}}
Tricarbonic acid
4
O
−
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
{\displaystyle {\ce {^{-}O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O^{-}}}}
Tetracarbonate
HO
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
OH
{\displaystyle {\ce {HO-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-OH}}}
Tetracarbonic acid
5
O
−
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
{\displaystyle {\ce {^{-}O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O^{-}}}}
Pentacarbonate
HO
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
OH
{\displaystyle {\ce {HO-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-OH}}}
Pentacarbonic acid
6
O
−
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
{\displaystyle {\ce {^{-}O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O^{-}}}}
Hexacarbonate
HO
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
O
−
C
O
‖
−
OH
{\displaystyle {\ce {HO-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-O-{\overset {\displaystyle O \atop \|}{C}}-OH}}}
Hexacarbonic acid
References [ edit ]
^ Bruna, Pablo J.; Grein, Friedrich; Passmore, Jack (2011). "Density functional theory (DFT) calculations on the structures and stabilities of [Cn 2n +1 ]2– and [Cn 2n +1 ]X2 polycarbonates containing chainlike (CO2 )n n = 2–6; X = H or Li)". Canadian Journal of Chemistry . 89 (6): 671–687. doi :10.1139/v11-039 . ^ Pope, Barry M.; Yamamoto, Yutaka; Tarbell, D. Stanley (1977). "Di-tert -Butyl Dicarbonate" . Organic Syntheses 57 : 45 Collected Volumes , vol. 6, 1988, p. 418^ Lewars, Errol (1996). "Polymers and oligomers of carbon dioxide: ab initio and semiempirical calculations". Journal of Molecular Structure: THEOCHEM . 363 (1): 1–5. doi :10.1016/0166-1280(95)04420-5 .
Common oxides Exotic oxides Polymers Compounds derived from oxides
