Intramolecular C-13 and H-2 isotope effects have been measured for unimolecular losses of ethene (the McLafferty rearrangement) from metastable molecular ions of 2-ethyl-1-phenylbutan-1-one, 3-ethylpentan-2-one and heptan-4-one. Primary and secondary deuterium isotope effects are observed at the gamma-(terminal) and beta-positions, respectively. Large primary C-13 isotope effects occur at beta-positions and for the gamma-positions of 3-ethylpentan-2-one and heptan-4-one. The carbon isotope effects in the cases of the doubly isotopically labelled CH3COCH(C2H5)(13CH2CH3) and CD3COCD(C2D5)(13CD2CD3) are 1.17 (+/- 0.01) and 1.04 (+/- 0.01), respectively. All of these isotope effects are consistent with a stepwise mechanism in which more than one step is rate determining.

Depending on the internal energy content, due to the operation of a geminal dialkyl effect, the Fe+-mediated dehydrogenation of alpha,alpha-dimethyl-substituted ketones preferably involves the more substituted alkyl chain.

AbstractCollisional activation of MeSOCH and PhCH2SOC̄HPh (but not PhSOCH) yields an ion of m/z 49, identified as HOS−. It is proposed that this ion is formed following proton transfer to oxygen followed by cyclization and elimination.

It is shown by field ionization kinetics that the ethene elimination from ionized 2-ethyl-butanoic acid is the most dominant channel at molecular ion lifetimes ⩽10−9 s. This channel, however, becomes rapidly less important with respect to ethyl elimination at molecular ion lifetimes ⪢10−9 s. Both eliminations occur without any detectable exchange between hydrogen or carbon atoms from different positions as shown by specific 2H- and 13C-labelling. The same observations are made for molecular ions decomposing in the metastable time frame of 10−6 to 10−5 s. On the basis of collision-induced dissociation experiments, it is demonstrated that ∼95% of the (MC2H5)+ ions have the structure of carbonyl oxygen-protonated crotonic acid which, in line with the 2H- and 13C-labelling, are formed by a successive, irreversible hydrogen shift from C-3 to the carbonyl oxygen and cleavage of the C-2C′-3 bond to eliminate ethyl. The remaining ∼5% of the (MC2H5)+ ions have the structure of carbonyl oxygen-protonated methacryclic acid. In line with the 2H- and 13C-labelling results, these ions are generated by a successive, irreversible hydrogen shift from C-3 to the carbonyl oxygen, migration of the C(OH)2 group from C-2 to C-3, a hydrogen shift from C-3 to C-2, and eventual cleavage of the C-2C′-3 bond to eliminate ethyl. Further metastable decompositions of the (MC2H5)+ ions correspond to eliminations of molecules of water, C2H2O, and C2H4O. The water molecule contains the original hydroxylic hydrogen and one of the hydrogen atoms of C-3. The eliminated C2H2O molecule contains the C-1 and C-2 atoms, while the eliminated C2H4O molecule contains the C-3 and C-4 atoms. Combined with the obtained 2H-labelling results, strong support, if not evidence, is provided for the intermediacy of ion/molecule complexes during the eliminations of C2H2O and C2H4O from the (MC2H5)+ ions.

ChemInformVolume 19, Issue 52 Preparative Organic Chemistry ChemInform Abstract: Combined 2H and 18O Isotope Effects in Support of a Concerted, Synchronous Elimination of Acetaldehyde from a Bis(benzyl ethyl ether) Radical Cation. C. E. ALLISON, C. E. ALLISON Dep. Org. Chem., Univ. Adelaide, Adelaide, South Aust. 5001, Aust.Search for more papers by this authorM. B. STRINGER, M. B. STRINGER Dep. Org. Chem., Univ. Adelaide, Adelaide, South Aust. 5001, Aust.Search for more papers by this authorJ. H. BOWIE, J. H. BOWIE Dep. Org. Chem., Univ. Adelaide, Adelaide, South Aust. 5001, Aust.Search for more papers by this authorP. J. DERRICK, P. J. DERRICK Dep. Org. Chem., Univ. Adelaide, Adelaide, South Aust. 5001, Aust.Search for more papers by this author C. E. ALLISON, C. E. ALLISON Dep. Org. Chem., Univ. Adelaide, Adelaide, South Aust. 5001, Aust.Search for more papers by this authorM. B. STRINGER, M. B. STRINGER Dep. Org. Chem., Univ. Adelaide, Adelaide, South Aust. 5001, Aust.Search for more papers by this authorJ. H. BOWIE, J. H. BOWIE Dep. Org. Chem., Univ. Adelaide, Adelaide, South Aust. 5001, Aust.Search for more papers by this authorP. J. DERRICK, P. J. DERRICK Dep. Org. Chem., Univ. Adelaide, Adelaide, South Aust. 5001, Aust.Search for more papers by this author First published: December 27, 1988 https://doi.org/10.1002/chin.198852075Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume19, Issue52December 27, 1988 RelatedInformation

The mechanisms of formation of the major product ions produced by collision activation of the enolate negative ion of 3,3-dimethylheptan-4-one have been studied by deuterium labelling. H2 loss involves 1,2-elimination from the 6- and 7-positions. Methane elimination is complex involving three competitive rearrangement processes. Ethene loss produces the most abundant fragment ion and occurs by elimination of the C1-C2 ethyl group with concomitant proton transfer from the 1-position. In the case of the enolate ion from CD3CH2CMe2COPr, the expected elimination of C2H2D2 competes with loss of C2H4 from positions 6 and 7. Other decompositions are as follows: loss of C3H8 involves the methyl and ethyl substituents at positions 7, 1 and 2 respectively; loss of C4H8 occurs by two processes, ( i ) successive losses of two C2H4 units (from the 1, 2 then 6, 7 positions), and (ii) loss of CH2=CMe2 (from the 2 and 3 positions); and loss of C5H12 produces Et-C=C-0-. .

AbstractThe prim. carbanion (III), which derives from the title compound (I), competitively eliminates C2H4 (stepwise) and C4H8 (via a rearrangement process).

AbstractThe collisional activation mass spectra of Et2CH‐COO‐, Me2CH‐COO‐, and Me3C‐COO‐ are different, all showing characteristic decompositions.

Treatment of laevulinic acid with N- methylaniline yields 1,5-dimethyl- 1H-1-benzazepin-2(3H)-one and 5-methyl-5-[4-( methylamino )phenyl]-1- phenylpyrrolidin-2-one. The structure of the latter is confirmed by a single-crystal X-ray study. The yield of benzazepinone is increased if either m- methoxy-N-methylaniline or m-methyl-N- methylaniline is allowed to react with laevulinic acid. Treatment of the benzazepinones with phosphoryl chloride in pyridine produces 2-chloro-1,5-dimethyl-1H-1- benzazepines in quantitative yields, but these compounds are highly reactive under acidic conditions, undergoing nucleophilic displacement at C2. In contrast, treatment of benzazepinones with neat phosphoryl chloride yields yellow dimers , assigned as 2′-chloro-1,1′,5,5′- tetramethyl-2,3′-bi-1H-1-benzazepines, and with stabilities only marginally greater than those of the 2-chloro-1,5-dimethyl-1H-1- benzazepines.

The (M – H+)− ion of butyrophenone undergoes the following reactions on collisional activation: losses of CH3•, CH4, (C,H5•), C2H4, C3H7•, (CO + CH4), together with formation of C6H5− and C4H5O−. Labelling studies (13C and 2H) show that the losses of CH3•, C3H7• and the formation of C6H5− and C4H5O− are specific and occur without hydrogen scrambling. All other reactions involve prior or accompanying hydrogen rearrangement. In particular, the loss of C2H4 is very complex: it involves loss of ethyl carbon atoms, but all hydrogen atoms are involved via specific rearrangement reactions. The phenyl–alkyl H rearrangements which are noted for this process occur after collisional activation of the (M – H+)− ion.

AbstractThe predominant processes are methane elimination involving the C ‐ 1(7) methyl group together with H ‐ 3(5) and the elimination of ethylene including γ‐Htransfer.

AbstractFür die Bildung der Verbindungen (V) und (VI) wird eine mechanistische Erklärung gegeben, derzufolge die Dihydrobenzazepinone (III) von POCl3 zuerst zu den Benzazepinen (IV) chloriert werden, die sich unter Umlagerung und HCl‐Eliminierung dimerisieren.

AbstractCollision‐induced dissociation of the ions [ArS]−, [ArSO]− and [ArSO2]− has uncovered a rich and varied ion chemistry. The major fragmentations of [ArS]− are complex and occur without prior ring hydrogen scrambling: for example, [C6H5S]−→[C2HS]− and [HS]−; [p‐CD3C6H4S]−→[C6H4S]−˙, [CD3C4S]− and [C2HS]−. In contrast, all decompositions of [C6H5CH2S]− are preceded by specific benzylic and phenyl hydrogen interchange reactions. [ArSO2]− and [ArSO2]− ions undergo rearrangement, e.g. [C6H5SO]−→[C6H5O]− and [C6H5S]−; [C6H5SO2]−→[C6H5O] −. The ion [C6H5CH2SO]− eliminates water, this decomposition is preceded by benzylic and phenyl hydrogen exchange.

Thioglycollates and β-thiopropionates with SH and/or CO2H groups yield pronounced (M-H)- ions in their negative ion spectra, not molecular negative ions as we previously reported. Compounds containing R1-S-CH2- functionality (R1 = alkyl or aryl) undergo α cleavage to S to yield R1S- and -S-CH2-ions. Hydrogen rearrangements are rare but thioglycollates R1SCH2CO2H characteristically eliminate R1SH to yield CH2CO2-. Fragment negative ions generally do not contain enough excess energy to allow decomposition, so we have studied their collision induced dissociations. Simple cleavage reactions are usual: for example BuSCH2CO2- decomposes to yield both BuS- and BuSCH2-. Group migration to sulfur is also observed; for example, ions -SCH2CO2R2 (R2 = alkyl or aryl) eliminate carbon dioxide to produce R2SCH2- as the major product.

Abstract3,6‐Dibrom‐ anthranilsäure (I) wird in Forum ihres Diazoniumsalzes (II) in Gegenwart von Furan (III) zugesetzt, wobei das Addukt (IV) über eine Dehydrobenzol‐Zwischenstufe erhalten wird.

The title compounds have been synthesised by sequences involving as the key step the trapping of arynes with furan.

The reaction of benzyne (generated by the thermolysis of o- diazoniobenzoate) with the following alkenes has been examined: 1,1-dichloroethene (5) (vinylidene chloride), 1,1-dichloro-propene (7), 1,1-dichloro-2-methylpropene (17), 2-methylprop-1-en-1-yl acetate (18) and 2-chloro-prop-2-enenitrile (α-chloroacrylonitrile) (22). Substituted bicyclo[4,2,0]octa-1,3,5-trienes resulting from 2+2 cycloaddition were obtained from (5), (7), and (22), while the reaction involving the en01 acetate (18) gave only 'ene' product, and that involving (17) gave an intractable mixture. (Z)- and (E)-1-Chloro-2-(o-chlorophenyl)propene were obtained as minor products in the reaction of benzyne with (7): these products result from a chlorine atom transfer to the aromatic ring, and a novel mechanism involving a diradical → carbene rearrangement is postulated.