2.2‐Dimethyl‐chinuclidon‐(6), ein mesomeriefreies Säureamid

Pracejus, H.

doi:10.1002/cber.19590920435

Cited by 82 publications

(35 citation statements)

References 17 publications

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“…Thus the +NH, substituent may be supposed to give an upward shift of at least 80 cm-l which would result in absorption around 1800 and 1760 cm-l for amides and urea, respectively, when protonated at the nitrogen. This is in excellent agreement with the value found for the N-triethylbenzamide cation (IV) which absorbs at 1783 cm-l and also for the hydrochloride of the non-mesomeric amide 2 : 2-dimethylquinuclidone-6 (VII) (1799 cm-l) [24]. In the latter case it is also clear that the effect of hydrogen bonding on the carbonyl band is not very large.…”

Section: B Infrared Spectrasupporting

confidence: 90%

“…The inductive effect has been shown [24] to account for a decrease of only 5.5 units in amides, so that the remaining lowering, which may be roughly put equal to 10 kcal/mole, should be due to the mesomeric effect. This value is therefore the lower limit for the resonance energy of amides and thioamides and, with a similar reasoning, twice this value should represent the lower limit for the resonance energy of (thio)urea.…”

Section: [9]mentioning

confidence: 99%

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The structure of protonated amides and ureas and their thio analogues

Janssen¹

1961

Spectrochimica Acta

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Abstrae~-T~e electronic absorption spectra, were studied of protonated thioamides and thioureas, as well aa the infra-red spectra of alkylated acetamide, thioacetamide, urea and thiourea and their hydrochlorides. All results consistently show that the proton is normally attached to the oxygen (or sulphur) atom. Earlier data pointing to the existence of the ammonium structure are reinterpreted. The resonance within these molecules appears to be the decisive factor in determining the site of protonation,

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Section: B Infrared Spectrasupporting

confidence: 90%

Section: [9]mentioning

confidence: 99%

The structure of protonated amides and ureas and their thio analogues

Janssen¹

1961

Spectrochimica Acta

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“…1 468 / 1.35 = 1 0 8 7 and 1 380 / 1.35 = 1 022 cnl-l. In addition the effect of a positive charge on the N atom \vould have a large inductive effect on the carbonyl group significantly raising its stretching frequency t o near 1 780 -1 800 cm-l, as has been described for N-aroyltrialkylainmonium halides (13), 2,2-dimethyl-6-quiiluclidone salts (14), and N-acyltrialkylammoniuin and N-acylpyridiniun~ halides (15). Alternative explanations must be sought for the 1468, 1380, and 1 112 cm-1 bands as will be described below.…”

mentioning

confidence: 81%

PROTONATED CARBONYL GROUPS: V. Α-Pyridone SALTS

Cook¹

1965

Can. J. Chem.

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Salts of 1-methyl-2-pyridone and 1-methyl-2-quinolone with strong acids have been prepared and their infrared spectra recorded between 4 000 and 650 cm−1. Protonation of the carbonyl group occurs giving rise to OH stretching, in-plane and out-of-plane bending vibrations which absorb in characteristic regions of the spectrum, namely 1 900 – 3 300 cm−1 (depending on the anion), ~ 1 250 cm−1, and ~ 800 cm−1 respectively, with appropriate shifts on deuteration. Other tentative assignments are made.

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“…It compares with, and supports, the result (pK BH ϩ ϭ 5.3) estimated by Pracejus for 6,6-dimethyl-1-azabicyclo[2,2,2]octan-2-one (7a), an amide whose bicyclic structure prevents appreciable resonance between the nitrogen and the carbonyl. [36] This difference of 4.37 in pK BH ϩ values between N-tritylacetamide and N-methylacetamide corresponds to δSB ϭ 24.9 kJ·mol…”

Section: Base Strengths Of N-acetylaminesmentioning

confidence: 98%