Weak bases in strong acids. V. Substituent effects in the formation of some protonated ketones and the corresponding carbonium ions

1970 ◽  
Vol 92 (6) ◽  
pp. 1770-1772 ◽  
Author(s):  
Edward M. Arnett ◽  
John V. Carter ◽  
Roderic P. Quirk
Keyword(s):  
Substituent Effects ◽  
Weak Bases ◽  
Carbonium Ions ◽  
Strong Acids

Effects of Medium and Substituents on Dissociationof 4,4'-Disubstituted Bis(benzenesulfon)imides

1996 ◽  
Vol 61 (8) ◽  
pp. 1205-1214 ◽  
Author(s):  
Miroslav Ludwig ◽  
Pavel Štverka
Keyword(s):  
Latent Variables ◽  
Dissociation Constants ◽  
Substituent Effects ◽  
Principal Component ◽  
H Nmr ◽  
Base Process ◽  
Elemental Analyses ◽  
Substituent Constants ◽  
Model Substances ◽  
Strong Acids

Ten 4,4'-disubstituted bis(arenesulfon)imides of the general formula XC6H4SO2NHSO2C6H4X have been synthesized and their structures confirmed by their 1H NMR spectra. Elemental analyses are presented for the compounds not yet described. The dissociation constants of these model substances have been measured potentiometrically in pyridine, dimethylformamide, methanol, ethanol, propylene carbonate, acetone, acetonitrile, 1,2-dichloroethane and tetramethylene sulfone. The pKHA values obtained have been correlated with three sets of the Hammett substituent constants and the results have been used to discuss the solvent and substituent effects on the dissociation of the compounds studied. Sulfonimides with electron-acceptor substituents behave as rather strong acids in some solvents (pyridine, dimethylformamide, methanol and ethanol), whereas normal substituent dependences are found in other solvents. The experimental data have also been interpreted with the help of the statistical methods based on latent variables. From the calculations it follows that only the first principal component, which correlates well with the substituent constant sets adopted, is statistically significant in describing the substituent effect on the acid-base process studied.

scholarly journals Utilization of Kalpataru Flower Extract (Hura crepitans Linn) as an Alternative Acid Base Indicator

2020 ◽  
Vol 9 (3) ◽  
pp. 148-157
Author(s):  
Bayu Riswanto ◽  
Sitti Aminah
Keyword(s):  
Strong Acid ◽  
Weak Acids ◽  
Acid Base ◽  
Flower Extract ◽  
Weak Bases ◽  
Base Solution ◽  
Acid Base Titration ◽  
Hura Crepitans ◽  
Dark Green ◽  
Strong Acids

Kalpataru flower (Hura crepitans Linn) is an anthocyanin-containing plant. This study aims to utilize extract from the kalpataru flower as an alternative acid base indicator and determine the type of acid-base titration suitable for extracting the kalpataru flower indicator. Kalpataru flowers are macerated with methanol solvent for around 2 hours. Kalpataru flower extract was tested as an indicator in acid-base solution, buffer, and compared with phenolphthalein and methyl orange for acid-base titration, namely: strong acids with strong bases, weak acids with strong bases, and weak bases with strong acids. The results obtained in this study were: indicator extract of brownish yellow kalpataru flowers, in strong red acids, in strong bases of dark green, in weak pink acids, and in weak bases in light green. In the buffer, the indicator extract of the kalpataru flower has a range of pH pH 4-5 (pink-colorless) and pH 9-11 (yellowish green-dark green). The indicator of kalpataru flower extract can be used on strong acid titration with strong bases, weak acids with strong bases and weak bases with strong acids. Kalpataru flower extract can be used as an acid-base indicator.

scholarly journals Kemampuan Siswa Memperoleh dan Memahami Konsep Hidrolisis Garam dalam Pembelajaran Menggunakan LKS Berbasis Belajar Penemuan pada Siswa Kelas XI SMAN 2 Palangka Raya Tahun Ajaran 2018/2019

2020 ◽  
Vol 1 (1) ◽  
pp. 16-29
Author(s):  
Riska Meilani Simanjuntak ◽  
Abudarin Abudarin ◽  
Karelius Karelius
Keyword(s):  
Discovery Learning ◽  
Research Subjects ◽  
Descriptive Research ◽  
Comprehension Test ◽  
Weak Bases ◽  
Three Stages ◽  
Strong Acids ◽  
Academic Year ◽  
Hydrolysis Of

Materi larutan merupakan materi yang sulit bagi kebanyakan siswa, salah satunya materi hidrolisis garam. Penelitian ini bertujuan untuk mendeskripsikan kemampuan siswa memperoleh dan memahami konsep hidrolisis garam dari asam kuat dan basa lemah dalam pembelajaran menggunakan LKS berbasis belajar penemuan. Penelitian ini merupakan penelitian deskriptif. Subyek penelitian adalah siswa kelas XI MIPA SMA Negeri 2 Palangka Raya tahun ajaran 2018/2019 yang berjumlah 36 siswa. Instrumen yang digunakan berupa soal tes pemahaman konsep (pretes dan postes) dan LKS berbasis belajar penemuan. Data dikumpulkan melalui tiga tahap, yakni pretes, pelaksanaan pembelajaran, dan postes. Hasil penelitian menunjukkan bahwa kemampuan siswa dalam memperoleh konsep hidrolisis garam dari asam kuat dan basa lemah dalam pembelajaran menggunakan LKS berbasis belajar penemuan tercermin dari jumlah siswa yang memperoleh konsep, yaitu rata-rata sebesar 82,64%. Pemahaman konsep siswa tentang hidrolisis garam dari asam kuat dan basa lemah dalam pembelajaran menggunakan LKS berbasis belajar penemuan rata-rata sebesar 89,81%.   Solution material is a difficult material for most students, one of which is salt hydrolysis. This study aims to describe the students' ability to obtain and understand the concept of salt hydrolysis from strong acids and weak bases in learning using discovery learning based worksheets. This research is a descriptive research. The research subjects were students of class XI MIPA at SMA Negeri 2 Palangka Raya in the 2018/2019 academic year, totaling 36 students. The instruments used were in the form of concept comprehension test questions (pretest and posttest) and discovery learning-based worksheets. Data were collected through three stages, namely pretest, implementation of learning, and posttest. The results showed that the students' ability to obtain the concept of hydrolysis of salt from strong acids and weak bases in learning using discovery learning-based worksheets was reflected in the number of students who obtained the concept, namely an average of 82.64%. Students' understanding of the concept of salt hydrolysis from strong acids and weak bases in learning using discovery-based worksheets an average of 89.81%.

Stabilities of Carbonium-Ions. IV. Steric Effects in the Solvolysis of Substituted Diphenylmethyl Chlorides

1986 ◽  
Vol 39 (4) ◽  
pp. 625 ◽  
Author(s):  
R Bolton ◽  
RE Burley ◽  
NJ Williams
Keyword(s):  
Electronic Effect ◽  
Substituent Effects ◽  
Methyl Chloride ◽  
Steric Effects ◽  
Methyl Groups ◽  
Hydrogen Atoms ◽  
Carbonium Ions ◽  
Rate Of Reaction ◽  
Resonance Stabilization ◽  
Planar Transition

The replacement of ortho-hydrogen atoms by methyl groups in diphenylmethyl chloride has three distinguishable results upon the rate of solvolysis . Firstly, the alkyl groupactivates by its electronic effect; secondly, steric interactions diminish all observed substituent effects regardless of the position of the substituent in the aryl system; and thirdly, steric acceleration of the solvolysis can be seen in the rate of reaction of bis (2,6-dimethylphenyl)methyl chloride. The ortho-methyl substituents inhibit the formation of the planar transition state necessary to allow the greatest resonance stabilization by the aryl substituents of the incipient carbocation. Greater degrees of twist are reflected both in the variations in the rates of solvolysis of the poly(orthomethyl ) diphenylmethyl chlorides and in the consistent fall in the value of p+ with successive ortho-substitution.

A MNDO study of planar thioacyl-substituted carbocations

1992 ◽  
Vol 70 (1) ◽  
pp. 111-115 ◽  
Author(s):  
Jack Leon Ginsburg ◽  
Richard Francis Langler ◽  
Raj Kumar Raheja ◽  
Laura Precedo
Keyword(s):  
Gas Phase ◽  
Substituent Effects ◽  
Mndo Method ◽  
Saturation Effect ◽  
Semiempirical Calculations ◽  
Isodesmic Reactions ◽  
Electron Population ◽  
Resonance Saturation ◽  
Carbonium Ions

Relative gas phase stabilities of pairs of planar regioisomeric thioacyl-substituted carbocations have been calculated using the MNDO method. These systems are stabilized by good π donors. The role of S π-electron population as a gauge of substituent effects is examined. Similar results were obtained using isodesmic reactions to gauge substituent effects. Results of this and earlier studies are consistent with the resonance saturation effect. Keywords: semiempirical calculations, carbonium ions.

NUCLEAR MAGNETIC RESONANCE STUDIES OF THE PROTONATION OF WEAK BASES IN FLUOROSULPHURIC ACID: II. AMIDES, THIOAMIDES, AND SULPHONAMIDES

1963 ◽  
Vol 41 (10) ◽  
pp. 2642-2650 ◽  
Author(s):  
T. Birchall ◽  
R. J. Gillespie
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Carbonyl Oxygen ◽  
Conclusive Evidence ◽  
Sulphur Atom ◽  
Magnetic Resonance Studies ◽  
Weak Bases ◽  
Strong Acids ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of solutions of amides in fluorosulphuric acid confirm previous results which indicated that protonation of amides occurs on the carbonyl oxygen. A similar study of solutions of thioacetamide, thioacetanilide, thiourea, and N-methylthiourea provides conclusive evidence that the sulphur atom is protonated in these bases. In the case of N-methyl- and N,N′-dimethyl-p-toluenesulphonamide and sulphamide protonation occurs on nitrogen rather than on oxygen. It was not possible to obtain any conclusive evidence on the site of protonation of urea and N,N′-dimethylurea. Evidence is presented which indicates that thiourea and N-methylthiourea are diprotonated in solution in strong acids such as fluorosulphuric acid, and diprotonation of urea and N,N′-dimethylurea under the same conditions also seems very likely.

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