An experimental and ab initio study of the addition of atomic carbon to water

Ahmed, Sheikh N.; McKee, Michael L.; Shevlin, Philip B.

doi:10.1021/ja00350a033

Cited by 35 publications

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“…[1] It is therefore surprising that an early (1983) conclusion by Ahmed, Shevlin, and McKee regarding these types of reactions was that the ground-state triplet 3 P does not react with water. [2] This was supported by 1) the computational (MP3/6-31G**//HF/3-21G + ZPVE) finding that the initial complex 1 of 3 P-C with water (Scheme 1) dissociates before the subsequent reaction to form hydroxymethylene (2) can occur due to the relatively high barrier for insertion of 3 P-C into an OÀH bond of water, and 2) the rationalization of experiments that should give formaldehyde (3) and subsequently short-chain sugar molecules only from singlet ( 1 D) carbon atoms (Scheme 2). [3] The reactions of small carbon clusters C n (n < 5) with water in Ar matrices also indicate that neither 3 P-C nor singlet or triplet C 2 react with water, while C 3 species do.…”

Section: S-c (233 Kcal Mol à1mentioning

confidence: 99%

“…Hence, on these high-level theoretical grounds, there seems to be no viable pathway for formation of 3 2 from the reaction of 3 P-C with water, in agreement with earlier conclusions derived from lower-level computations. [2] Even if 3 2 were to form through an undiscovered reaction channel, it is unlikely to react as a triplet to form triplet formaldehyde ( ) due to the exothermicity of this OÀH insertion reaction (76.1 kcal mol À1 ). This excess energy will also help overcome the barrier for the further rearrangements of 1 2-anti to formaldehyde 1 3 or 1 2-syn.…”

mentioning

confidence: 99%

“…Hence, based on earlier and our present computations, only singlet carbon atoms should react with water to give formaldehyde. [2] It will therefore be crucial to determine the multiplicity of carbon atoms generated in our experiments and to assure that the reactions of singlet and triplet carbon atoms can clearly be differentiated.…”

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confidence: 99%

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The “Non‐Reaction” of Ground‐State Triplet Carbon Atoms with Water Revisited

Schreiner¹,

Reisenauer²

2006

ChemPhysChem

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We introduce a novel experimental setup for the generation of carbon atoms by means of pulsed laser ablation with a pulse rate optimized to avoid warming of the matrix. The combination of this technique with annealing of the matrix, recooling, and spectral recording (e.g. IR) allowed us to differentiate between the reactivity of triplet and singlet carbon atoms towards water under matrix-isolation conditions. Our experimental procedure assures the relaxation of all unreacted carbon atoms to their triplet ground state in the 10 K matrix before spectral recording. In agreement with CCSD(T)/cc-pVTZ+ZPVE computational data and earlier lower level results, we find that triplet carbon atoms indeed do not react with water, despite their high initial energy. Intersystem crossing of the triplet to singlet states of hydroxy carbene are less important, as the barriers for rearrangement of the initial complex of triplet carbon atoms and water to covalently bound species are too high, and dissociation is more likely. We found no evidence for a direct O--H bond-insertion path for triplet carbon atoms. Self-condensation reactions of triplet carbon atoms are clearly favored and yield carbon clusters that show reactivity of their own. The proposed formation of aldoses in extraterrestrial environments can therefore only derive from "hot" carbon atoms or through photoreactions.

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Section: S-c (233 Kcal Mol à1mentioning

confidence: 99%

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confidence: 99%

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The “Non‐Reaction” of Ground‐State Triplet Carbon Atoms with Water Revisited

Schreiner¹,

Reisenauer²

2006

ChemPhysChem

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“…The aqueous phase was extracted with ethyl ether (3 X 25 mL) and the combined extracts were washed with 50 mL of saturated aqueous sodium bicarbonate, 50 mL of water, and 50 mL of saturated aqueous sodium chloride and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to give 0.69 g (87%) of a 1 : I mixture of octalins 62 and 63, which could not be separated; ir (CC1,): 1670 cm-'; 'H nmr (CDCI,) 6: 0.77 (s, 3H), 0.80 (d, J = 6.5 Hz, 3H) 0.84 (s, 3H), 1.64 (bs, 3H), 4.98 and 5.21 (broad singlets for 6 3 and 62, respectively, 1H); ms rnle (relative intensity): 55 (29), 67 (34), 79(28), 9 l(30). l09( 100).…”

Section: P9p Iop-tritnethyl-2-decalone (60)mentioning

confidence: 99%

“…The latter condition was expected to be fulfilled by the fact that conformation 8 should be the preferred one, due to an unfavourable 1,3-diaxial interaction between methyl groups in the other chair conformer (9)," and by the fact that in conformer 8 the carbene and the methyl into which insertion is desired are within bonding distance of each other. 12 In spite of these encouraging considerations, however, it was apparent from the outset that a source of naked carbon atoms woud not be synthetically useful for this purpose in light of the high reactivity and low selectivity of this simplest of all organic reactive intermediates (29). We therefore sought a less direct means of accomplishing the desired, carbon atom insertion.…”

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confidence: 99%

Carbon atom insertion bicycloannulation: total syntheses of ishwarane and ishwarone

Cory¹,

Burton²,

Chan³

et al. 1984

Can. J. Chem.

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. Can. J. Chem. 62, 1908Chem. 62, (1984. insertion of a carbon atom into a methyl cyclohexene, leading in a single synthetic step to a bicyclo[3.2. I .02.']octane by carbene addition to the double bond and carbene insertion into a methyl C-H bond, has been accomplished by treating the cyclohexene with carbon tetrabromide and methyllithium at low temperatures. This new bicycloannulation method has been employed in a total synthesis of ishwarane (I), the naturally occurring parent hydrocarbon of the ishwarane class of tetracyclic sesquiterpenes. Although this reaction was not successful with various possible precursors of ishwarone (2), this natural product was prepared in low yield by a two-step version of the carbon atom insertion bicycloannulation (CAiB) procedure involving addition of bromoform-derived dibromocarbene to the octalone (5) followed by treatment of the resulting dibromocyclopropane (56) with methyllithiurn. The same two-step sequence was also successful in the first synthesis of norishwarane (20), the hydrocarbon comprising the bare ring system of the ishwarane sesquiterpenoids. The Diels-Alder synthesis used in the preparation of the octalin precursor (18) of norishwarane could not be used for the terpenes themselves because of the lack of dienophilic reactivity of the required cyclohexenone (7). A regioselective Diels-Alder equivalent sequence was therefore developed, consisting of conjugate addition of lithium di(3-methyl-3-buteny1)cuprate (42) to 2,3,4-trimethylcyclohex-Zen-I-one (7), epoxidation, base-catalyzed cyclization of the resulting epoxide (47) to a mixture of primary and tertiary alcohols (50 and 49, respectively), and dehydration of 49 to give 5. In the case of ishwarane, the octalin precursor (62) was synthesized by conjugate addition of lithium dimethylcuprate to octalone 59, addition of methyl magnesium bromide to the resulting decalone (60) to give octalol 61, and dehydration. Chem. 62, 1908Chem. 62, (1984.En faisant rkagir le cyclohexkne avec le titrabromure de carbone et le mCthyllithium a basse tempkrature, on a rtalisC I'insertion d'un atome de carbone dans le mCthylcyclohexkne; on a ainsi obtenu en une seule Ctape le bicyclo[3.2.1 .02.']octane par I'addition de carbene sur la double liaison et par une insertion de carbkne dans une liaison C-H du mithyle. OR a utilisee cette nouvelle methode de bicycloannellation dans une synthttse totale de I'ishwarane (I), I'hydrocarbure naturel parent des sesquiterpknes tetracycliques de la classe de I'ishwarane. Bien que cette reaction n'aie pas pu &tre appliquCe avec succes i divers precurseurs possibles de I'ishwarone (2), on a prepare ce produit naturel avec un faible rendement en faisant appel a une version en deux Ctapes de la mtthode de bicycloannellation par insertion d'un atome de carbone (BIAC) impliquant une addition d'un dibromocarbkne, provenant du bromoforme, sur I'octalone (51, puis une reaction du dibromocyclopropane (56) qui en rtsulte avec du mCthyllithium. On a aussi utilist cette mCthode avec succks pour realiser ...

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Tunneling in the Reactions of Carbenes and Oxacarbenes

Gerbig

Schreiner

2013

Contemporary Carbene Chemistry

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An experimental and ab initio study of the addition of atomic carbon to water

Cited by 35 publications

References 0 publications

The “Non‐Reaction” of Ground‐State Triplet Carbon Atoms with Water Revisited

The “Non‐Reaction” of Ground‐State Triplet Carbon Atoms with Water Revisited

Carbon atom insertion bicycloannulation: total syntheses of ishwarane and ishwarone

Tunneling in the Reactions of Carbenes and Oxacarbenes

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