Temat: acidity - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Wpływ wiązań wodorowych na kwasowość związków chemicznych
The influence of hydrogen bonding on the acidity of chemical compounds
Autorzy:: Brzeski, Jakub
Makowski, Mariusz
Tematy:: wiązanie wodorowe
kwasowość
skala kwasowości
hydrogen bonding
acidity
acidity scale; Pokaż więcej
Wydawca:: Polskie Towarzystwo Chemiczne
Powiązania:: https://bibliotekanauki.pl/articles/972277.pdf Link otwiera się w nowym oknie
Opis:: Both intra- and intermolecular hydrogen bonds increase the acidity of the systems in which they occur. Stabilization of the anion formed after deprotonation with a single intramolecular hydrogen bond causes a significant increase in the strength of acid in question, compared to the system in which such interaction does not exist. Hydrogen bonds, through their influence on the acid-base properties of chemical compounds, play a key role in organic chemistry, coordination chemistry, biochemistry and medicine. This paper comprise a review of the most important publications on the impact of hydrogen bonds on the acidity of chemical compounds and the relationship between the specificity of hydrogen bonds and the strength of the resulting acid. The relationship between intermolecular hydrogen bond energy and the pK_a value of a given complex is thoroughly discussed in this paper. It turns out that the energy of the hydrogen bond is not related to a single value of pK_a of neither the donor nor acceptor of this bond, but rather to the relative difference of these quantities. Namely, the strongest bonds are formed between those systems for which the pK_a’s of a donor and acid conjugated to an acceptor differ the least. The feature that clearly correlates with the pK_a value of the acid turns out to be the hydrogen bond length. The results of crystallographic studies have shown that the pK_a values of C-H acids strongly correlate with the length of C-H ••• O hydrogen bonds. It is worth noting here that the correlation is much better for systems in which the formation of a hydrogen bond is not sterically hindered. In the abundance of donor and acceptor groups in the structure of an acid and its corresponding base, the anion formed after deprotonation is stabilized by phenomenon known as networking. Spreading the negative charge over a larger area of the molecule increases the stability of the anion and thus significantly increases the strength of the corresponding acid. Acids, whose acidity is mainly based on the networking are called SHEAs (single-centered hydrogen-bonded enhanced acidity acids). In addition, the effect of hydrogen bonds on the acidity of specific biochemical systems, namely nucleobases, has been discussed based on the papers by Wetmore and collaborators. It turns out that intra- and extracellular water molecules should not be overlooked when assessing the acidity of biomolecules.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Acid properties of NaKH-ferrierites of various exchange degrees studied by IR spectroscopy
Autorzy:: Kawałek, Marek
Góra-Marek, Kinga
Datka, Jerzy
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 3.

Tytuł:: Acid properties of NaKH-ferrierites of various exchange degrees studied by IR spectroscopy
Autorzy:: Kawałek, Marek
Góra-Marek, Kinga
Datka, Jerzy
Opis:: The H/Na,K exchange was studied as one of the methods of modification of the acid properties of ferrierite. The concentration of Brönsted acid sites was determined, their acid strength and heterogeneity were followed by quantitative IR studies of ammonia desorption. The information on the Si status was obtained in MAS NMR experiments. IR studies showed that, even at low exchange degrees, hydroxyl groups both in 10-ring channels and in ferrierite cages were formed. In all the NaKH-ferrierites studied the concentration of Brönsted sites determined in our IR studies was practically identical as the concentration calculated from the zeolite composition. The acid strength of OH groups was found to increase with the H/Na,K exchange degree. The IR experiments of ammonia desorption evidenced that SiOHAl groups in our H-ferrierite were heterogeneous and several kinds of OH groups of various acid strength were found. It is possible that an increase of the acid strength with the exchange degree, i.e. with the amount of protons introduced is realized by the formation of less acidic hydroxyl groups at lower exchange degree, and more acidic hydroxyl groups at higher exchange degrees.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 4.

Tytuł:: Ocena aktywności ureazy glebowej w otoczeniu drzew rodziny orzechowate (Juglandaceae)
Evaluation of soil urease activity in the vicinity of trees of the family Nut (Juglandaceae)
Autorzy:: Bucki, Marek
Opis:: Część literaturowa pracy zawiera charakterystykę gleby, jej definicję, funkcje. Opisano czynniki glebotwórcze wraz z omówieniem ich wpływu na proces glebotwórczy oraz wskazano charakterystyczne właściwości gleby: odczyn i właściwości buforowe.Przedstawiono specyfikę działania enzymów jako biokatalizatorów wraz z omówieniem czynników wpływających na ich aktywność. Omówiono rolę enzymów glebowych. Opisano cykl obiegu azotu w biosferze z zaznaczeniem roli ureazy w tym cyklu. Przedstawiono pochodzenie, budowę i znaczenie ureazy w środowisku. Podano ogólne informacje o roślinach z rodziny orzechowate (Juglandacea).Celem pracy było określenie wpływu orzecha włoskiego na aktywność ureazy glebowej w jego otoczeniu. Aktywność ureazy oznaczano spektrofotometryczną metodą fenolowo-podchlorynową a kwasowość czynną i kwasowość wymienną gleby metodą wg standardu WRB. Wykazano, iż aktywność ureazy jest wyższa poza zasięgiem korony drzewa niż w obszarze jej działania. Największą różnicę w aktywności ureazy pod i poza koroną drzewa, zaobserwowano dla najstarszego drzewa a analizowanej grupy. Z kolei najsłabszą różnicę wykazały próbki odpowiadające najmniejszemu drzewu. Wskazuje to na fakt, iż rozbudowanie systemu korony i korzeni ma wpływ na ilość wydzielanego inhibitora ureazy. Otrzymane wyniki pokazały, że drzewa orzecha włoskiego wpływają negatywnie na aktywność ureazy w swoim otoczeniu.
The literature part of the work contains the characteristics of the soil, its definition and functions. The soil-forming factors have been described along with their effects on the soil-forming process and the soil characteristics are presented: pH factor and buffer properties. The specificity of enzymes as biocatalysts is discussed and the factors influencing their activity are described. The role of soil enzymes has been discussed. A cycle of nitrogen circulation in the biosphere has been described. The role of urease in this cycle was highlighted. The origin, structure and importance of urease in the environment are described. General information about the Juglandacea family was given. The aim of the study was to determine the effect of walnut trees on the activity of soil urease in the environment. Urease activity was determined by spectrophotometric phenol-hypochlorite method and active acidity and soil exchange acidity were measured following the WRB standard.It has been shown that soil urease activity is higher in the area outside of the tree crow than the range of the tree crown. The greatest difference in urease activity under and beyond the crown of a tree was observed for the oldest tree and the analyzed group. In turn, the weakest difference was found in samples corresponding to the youngest/smallest tree. This indicates that the development of the crown and root system increases the amount of secreted juglone. Juglone as urease inhibitor slow down its activity. The negative influence of juglone on urease is as more effective as higher is content of the inhibitor.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 5.

Tytuł:: Environmental evaluation with chemical sensors in the Palace Museum of Wilanow
Autorzy:: Pena-Poza, J.
Garcia-Heras, M.
Palomar, T.
Laudy, A.
Modzelewska, E.
Villegas, M.
Tematy:: heritage
sensor
acidity
temperature
sol-gel
Wilanów; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/200179.pdf Link otwiera się w nowym oknie
Opis:: Environmental evaluation arises as an innovative procedure to carry out preventive conservation of Cultural Heritage items. Parameters contributing to the proper conservation of such items can be monitored and assessed. Chemical sensors with optical response synthesised by the sol-gel method are useful for a complete and accurate environmental evaluation. Physical-chemical mechanisms of decay and degradation of materials can be predicted from the sensors response, which will favour the decisions on the adequate procedures to avoid damage. Sol-gel sensors prepared and applied in the present work are reversible, reusable and regenerable. Their optical response provides a change of colour vs. the parameters to which they are sensitive. Both temperature and environmental acidity have been monitored in several selected chambers of the Palace Museum of Wilanów (Warsaw, Poland). The optical response of sensors was recorded by visible spectrophotometry from June 2010 to December 2010. The results inform on the environmental conservation conditions, both indoor and outdoor the Palace. Main innovation of the research carried out concerns the evaluation of the environmental acidity as an essential parameter to be taken into account for the proper conservation that can not be measured by conventional methods.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: In situ thermogravimetry in an infrared spectrometer : an answer to quantitative spectroscopy of adsorbed species on heterogeneous catalysts
Autorzy:: Chevreau, Thérèse
Aiello, Sebastien
Gil, Barbara
Thibault-Starzyk, Frédéric
Gilson, Jean-Pierre
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 7.

Tytuł:: Light, earthworms, and soil resources as predictors of diversity of 10 soil invertebrate groups across monocultures of 14 tree species
Autorzy:: Chorover, Jon
Chadwick, Oliver A.
Hale, Cynthia M.
Kasprowicz, Marek
Hobbie, Sarah E.
Trocha, Lidia K.
Wierzbicka, Anna
Dobies, Tomasz
Sobczyk, Łukasz
Weiner, January
Rożen, Anna
Jagodziński, Andrzej M.
Kałucka, Izabela
Reich, Peter B.
Modrzyński, Jerzy
Stasińska, Małgorzata
Mueller, Kevin E.
Skorupski, Maciej
Eisenhauer, Nico
Oleksyn, Jacek
Kieliszewska-Rokicka, Barbara
Opis:: Management of biodiversity and ecosystem services requires a better understanding of the factors that influence soil biodiversity. We characterized the species (or genera) richness of 10 taxonomic groups of invertebrate soil animals in replicated monocultures of 14 temperate tree species. The focal invertebrate groups ranged from microfauna to macrofauna: Lumbricidae, Nematoda, Oribatida, Gamasida, Opilionida, Araneida, Collembola, Formicidae, Carabidae, and Staphylinidae. Measurement of invertebrate richness and ancillary variables occurred ~34 years after the monocultures were planted. The richness within each taxonomic group was largely independent of richness of other groups; therefore a broad understanding of soil invertebrate diversity requires analyses that are integrated across many taxa. Using a regression-based approach and ~125 factors related to the abundance and diversity of resources, we identified a subset of predictors that were correlated with the richness of each invertebrate group and richness integrated across 9 of the groups (excluding earthworms). At least 50% of the variability in integrated richness and richness of each invertebrate group was explained by six or fewer predictors. The key predictors of soil invertebrate richness were light availability in the understory, the abundance of an epigeic earthworm species, the amount of phosphorus, nitrogen, and calcium in soil, soil acidity, and the diversity or mass of fungi, plant litter, and roots. The results are consistent with the hypothesis that resource abundance and diversity strongly regulate soil biodiversity, with increases in resources (up to a point) likely to increase the total diversity of soil invertebrates. However, the relationships between various resources and soil invertebrate diversity were taxon-specific. Similarly, diversity of all 10 invertebrate taxa was not high beneath any of the 14 tree species. Thus, changes to tree species composition and resource availability in temperate forests will likely increase the richness of some soil invertebrates while decreasing the richness of others.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 8.

Tytuł:: Impact of ultrasounds on physicochemical characteristics of potato tubers
Wpływ ultradźwięków na fizykochemiczne właściwości bulw ziemniaka
Autorzy:: Sawicka, B.
Pszczółkowski, P.
Danilčenko, H.
Jariene, E.
Tematy:: tuber
acidity
dry matter
starch
texture
ultrasound
potato; Pokaż więcej
Wydawca:: Uniwersytet Przyrodniczy w Lublinie. Wydawnictwo Uniwersytetu Przyrodniczego w Lublinie
Powiązania:: https://bibliotekanauki.pl/articles/13099236.pdf Link otwiera się w nowym oknie
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Positive and Negative Effects of Addition of Organic Carbon and Nitrogen for Management of Sulfuric Soil Material Acidity under General Soil Use Conditions
Autorzy:: Michael, Patrick S.
Tematy:: acidity management
organic carbon
organic nitrogen
organic matter; Pokaż więcej
Wydawca:: Uniwersytet Marii Curie-Skłodowskiej. Wydawnictwo Uniwersytetu Marii Curie-Skłodowskiej
Powiązania:: https://bibliotekanauki.pl/articles/2088183.pdf Link otwiera się w nowym oknie
Opis:: This paper reports the findings of two studies conducted to investigate the effects on pH, Eh and sulfate content of sulfuric soil material of acid sulfate soil following the addition of organic carbon and nitrogen. The first study compared the responses to simple carbon sources (glucose, sodium acetate and molasses) with complex organic matter in the form of chopped Phragmites. The second experiment considered the effect of nitrogen by testing organic matter with varying nitrogen content. The results of the first study showed that the changes in Eh and sulfate contents induced by these treatments mirrored the changes in pH, the highest change being only 5.6 units induced by sodium acetate. These results showed that organic carbon alone was ineffective in treating sulfuric soil material acidity, and that nitrogen was needed. Lucerne hay which had the highest nitrogen content produced the largest increase in pH by 4.2 units, and the changes of pea straw and wheat straw was 3.2 units. It was proposed that the alkalinising effect of the treatments was mediated by anaerobic microbial metabolism which required sources of nitrogen as well as organic carbon. The changes in soil redox conditions by -150 mV measured indicated that sulfur-reducing bacteria induced the changes in Eh, which caused pH to increase and sulfate content to decrease in comparison with nitrate-reducing bacteria. The findings of these studies have implications for management of sulfuric soil material acidity.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: IR studies of OH groups in mesoporous aluminosilicates
Autorzy:: Góra-Marek, Kinga
Datka, Jerzy
Opis:: The properties of acidic hydroxyl groups and Lewis acid sites in amorphous mesoporous aluminosilicates was followed by quantitative IR studies of ammonia adsorption and by low temperature studies of CO adsorption. We studied aluminosilicates synthesized by three methods: via atrane complexes, by grafting aluminium onto the siliceous material (HMCM-48) and in aqueous solution following a typical synthesis procedure (HMCM-41). IR spectra of OH groups showed weak but well seen band of Si-(OH)-Al groups at $3600–3610cm^{-1}$. The post-synthesis grafting of Al into MCM-48 was found to be the most effective way to produce mesoporous material with large content of Brønsted acid sites. IR studies have shown that the stoichiometry of dehydroxylation of the amorphous mesoporous materials was different than for zeolites: in mesoporous materials one Brønsted site lost created one Lewis acid site. IR experiments of CO sorption evidenced that generally two kinds of Si-(OH)-Al groups exist in mesoporous aluminosilicates: weakly acidic ones of $\Delta v_{OH\cdots CO} \approx160cm^{-1}$ (similar to that in zeolite NaHX), present in all the materials, hydroxyls of moderate acidity of $\Delta v_{OH\cdots CO} \approx200cm^{-1}$ (acid strength intermediate between that in zeolites NaHX and NaHY) present in HMCM-41 and HMCM-48, or hydroxyls of high acidity of $\Delta v_{OH\cdots CO} \approx300cm^{-1}$ (similar to that in highly siliceous zeolite HZSM-5) present in aluminoslicate prepared via atrane complexes method. This method of synthesis was found to be the most effective in preparation of mesoporous aluminosilicates with the strongest Brønsted acid sites. The weakly acidic hydroxyls in mesoporous aluminosilicates are very prone to dehydroxylation, they are lost at as low temperature as 800 K, hydroxyls of moderate, or high acidity are resistant to dehydroxylation and behave like zeolitic OH groups.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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