Carbon–oxygen bond

A carbon–oxygen bond is a covalent bond between carbon and oxygen. ^[1] ^[2] ^[3] Oxygen has 6 valence electrons and prefers to either share two electrons in bonding with carbon, leaving the 4 nonbonding electrons in 2 lone pairs :O: or to share two pairs of electrons to form the carbonyl functional group. =O: Simple representatives of these two bond types are the ^_OH in alcohols such as the ethanol in beverages and fuels and the C=O in ketones (as well as many other related carbonyl compounds).^[4]

Electronegativities and bond lengths

The C–O bond is strongly polarized towards oxygen (electronegativity of C vs O, 2.55 vs 3.44). Bond lengths for paraffinic C–O bonds are in the range of 143 picometer – less than those of C–N or C–C bonds. Shortened single bonds are found with carboxylic acids (136 pm) due to partial double bond character and elongated bonds are found in epoxides (147 pm).^[5] The C–O bond strength is also larger than C–N or C–C. For example, bond strengths are 91 kilocalories (380 kJ)/mol (at 298 K) in methanol, 87 kilocalories (360 kJ)/mol in methylamine, and 88 kilocalories (370 kJ)/mol in ethane.^[5]

Carbon and oxygen form terminal double bonds in functional groups collectively known as carbonyl compounds to which belong such compounds as ketones, esters, carboxylic acids and many more. Internal C=O bonds are found in positively charged oxonium ions. In furans, the oxygen atom contributes to pi-electron delocalization via its filled p-orbital and hence furans are aromatic. Bond lengths of C=O bonds are around 123 pm in carbonyl compounds. The C=O bond length in carbon dioxide is 116 pm. The C=O bonds in acyl halides have partial triple bond character and are subsequently very short: 117 pm. Compounds with formal C–O triple bonds do not exist except for carbon monoxide, which has a very short, strong bond (112.8 pm). Such triple bonds have a very high bond energy, even higher than N–N triple bonds.^[6] Oxygen can also be trivalent, for example in triethyloxonium tetrafluoroborate.

Chemistry

Carbon–oxygen bond forming reactions are the Williamson ether synthesis, nucleophilic acyl substitutions and electrophilic addition to alkenes. The Paternò–Büchi reaction involves carbonyl compounds.

Oxygen functional groups

Carbon–oxygen bonds are present in these functional groups:

Chemical class	Bond order	Formula	Example
Alcohols	1	R₃C–OH	Ethanol
Ethers	1	R₃C–O–CR₃	Diethyl ether
Peroxides	1	R₃C–O–O–CR₃	Di-tert-butyl peroxide
Esters	1	R₃C–CO–O–CR₃	Ethyl acrylate
Carbonate esters	1	R₃C–O–CO–O–CR₃	Ethylene carbonate
Ketones	2	R₃C–CO–CR₃	Acetone
Aldehydes	2	R₃C–CHO	Acrolein
Furans	1.5		Furfural
Pyrylium salts	1.5		Anthocyanins

CH				He
CLi	CBe	CB	CC	CN	CO	CF	Ne
CNa	CMg	CAl	CSi	CP	CS	CCl	CAr
CK	CCa	CSc	CTi	CV	CCr	CMn	CFe	CCo	CNi	CCu	CZn	CGa	CGe	CAs	CSe	CBr	CKr
CRb	CSr	CY	CZr	CNb	CMo	CTc	CRu	CRh	CPd	CAg	CCd	CIn	CSn	CSb	CTe	CI	CXe
CCs	CBa		CHf	CTa	CW	CRe	COs	CIr	CPt	CAu	CHg	CTl	CPb	CBi	CPo	CAt	Rn
Fr	CRa	Rf	Db	CSg	Bh	Hs	Mt	Ds	Rg	Cn	Nh	Fl	Mc	Lv	Ts	Og
	↓
	CLa	CCe	CPr	CNd	CPm	CSm	CEu	CGd	CTb	CDy	CHo	CEr	CTm	CYb	CLu
	Ac	CTh	CPa	CU	CNp	CPu	CAm	CCm	CBk	CCf	CEs	Fm	Md	No	Lr

**Chemical bonds to carbon**
Core organic chemistry	Many uses in chemistry
Academic research, but no widespread use	Bond unknown

References

↑ Organic Chemistry John McMurry 2nd Ed.
↑ March, J.; Smith, D. (2001). Advanced Organic Chemistry, 5th ed. New York: Wiley.
↑ Advanced Organic Chemistry Carey, Francis A., Sundberg, Richard J. 5th ed. 2007
↑ Clark, Jim (2000). "Bonding in Carbonyl Compounds". ChemGuide. Jim Clark. Retrieved 12 June 2014.
1 2 CRC Handbook of Chemistry and Physics 65Th Ed.
↑ Standard Bond Energies, Department of Chemistry, Michigan State University

Oxygen compounds

AgO Al₂O₃ AmO₂ Am₂O₃ As₂O₃ As₂O₅ Au₂O₃ B₂O₃ BaO BeO Bi₂O₃ BiO₂ Bi₂O₅ BrO₂ Br₂O₃ Br₂O₅ CO CO₂ C₂O₃ CaO CaO₂ CdO CeO₂ Ce₂O₃ ClO₂ Cl₂O Cl₂O₃ Cl₂O₄ Cl₂O₆ Cl₂O₇ CoO Co₂O₃ Co₃O₄ CrO₃ Cr₂O₃ Cr₂O₅ Cr₅O₁₂ CsO₂ Cs₂O₃ CuO D₂O Dy₂O₃ Er₂O₃ Eu₂O₃ F₂O F₂O₂ F₂O₄ FeO Fe₂O₃ Fe₃O₄ Ga₂O Ga₂O₃ GeO GeO₂ H₂O H₂¹⁸O H₂O₂ HfO₂ HgO Hg₂O Ho₂O₃ I₂O₄ I₂O₅ I₂O₆ I₄O₉ In₂O₃ InO₂ KO₂ K₂O₂ La₂O₃ Li₂O Li₂O₂ Lu₂O₃ MgO Mg₂O₃ MnO MnO₂ Mn₂O₃ Mn₂O₇ MoO₂ MoO₃ Mo₂O₃ NO NO₂ N₂O N₂O₃ N₂O₄ N₂O₅ NaO₂ Na₂O Na₂O₂ NbO NbO₂ Nd₂O₃

Chemical formulas

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CH																	He
CLi	CBe											CB	CC	CN	CO	CF	Ne
CNa	CMg											CAl	CSi	CP	CS	CCl	CAr
CK	CCa	CSc	CTi	CV	CCr	CMn	CFe	CCo	CNi	CCu	CZn	CGa	CGe	CAs	CSe	CBr	CKr
CRb	CSr	CY	CZr	CNb	CMo	CTc	CRu	CRh	CPd	CAg	CCd	CIn	CSn	CSb	CTe	CI	CXe
CCs	CBa		CHf	CTa	CW	CRe	COs	CIr	CPt	CAu	CHg	CTl	CPb	CBi	CPo	CAt	Rn
Fr	CRa		Rf	Db	CSg	Bh	Hs	Mt	Ds	Rg	Cn	Nh	Fl	Mc	Lv	Ts	Og
		↓
		CLa	CCe	CPr	CNd	CPm	CSm	CEu	CGd	CTb	CDy	CHo	CEr	CTm	CYb	CLu
		Ac	CTh	CPa	CU	CNp	CPu	CAm	CCm	CBk	CCf	CEs	Fm	Md	No	Lr

CH																	He
CLi	CBe											CB	CC	CN	CO	CF	Ne
CNa	CMg											CAl	CSi	CP	CS	CCl	CAr
CK	CCa	CSc	CTi	CV	CCr	CMn	CFe	CCo	CNi	CCu	CZn	CGa	CGe	CAs	CSe	CBr	CKr
CRb	CSr	CY	CZr	CNb	CMo	CTc	CRu	CRh	CPd	CAg	CCd	CIn	CSn	CSb	CTe	CI	CXe
CCs	CBa		CHf	CTa	CW	CRe	COs	CIr	CPt	CAu	CHg	CTl	CPb	CBi	CPo	CAt	Rn
Fr	CRa		Rf	Db	CSg	Bh	Hs	Mt	Ds	Rg	Cn	Nh	Fl	Mc	Lv	Ts	Og
		↓
		CLa	CCe	CPr	CNd	CPm	CSm	CEu	CGd	CTb	CDy	CHo	CEr	CTm	CYb	CLu
		Ac	CTh	CPa	CU	CNp	CPu	CAm	CCm	CBk	CCf	CEs	Fm	Md	No	Lr

Carbon–oxygen bond

Electronegativities and bond lengths

Chemistry

Oxygen functional groups

See also

References

CH																	He
CLi	CBe											CB	CC	CN	CO	CF	Ne
CNa	CMg											CAl	CSi	CP	CS	CCl	CAr
CK	CCa	CSc	CTi	CV	CCr	CMn	CFe	CCo	CNi	CCu	CZn	CGa	CGe	CAs	CSe	CBr	CKr
CRb	CSr	CY	CZr	CNb	CMo	CTc	CRu	CRh	CPd	CAg	CCd	CIn	CSn	CSb	CTe	CI	CXe
CCs	CBa		CHf	CTa	CW	CRe	COs	CIr	CPt	CAu	CHg	CTl	CPb	CBi	CPo	CAt	Rn
Fr	CRa		Rf	Db	CSg	Bh	Hs	Mt	Ds	Rg	Cn	Nh	Fl	Mc	Lv	Ts	Og
		↓
		CLa	CCe	CPr	CNd	CPm	CSm	CEu	CGd	CTb	CDy	CHo	CEr	CTm	CYb	CLu
		Ac	CTh	CPa	CU	CNp	CPu	CAm	CCm	CBk	CCf	CEs	Fm	Md	No	Lr