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Gibbs energy
No full textU ovom završnom radu opisana je slobodna Gibbsova energija, koje su karakteristike i kako se ponaša pri određenim uvijetima. Slobodna Gibbsova energija dobila je ime po američkom fizičaru i kemičaru Josiah Willard Gibbs. Gibbs je proučavao kemijske reakcije te odnos sustava reakcije i okoline. Uočio je što je slobodna energija, koji su kriteriji spontanosti reakcija te pri kojim uvijetima se moţe izračunati promjena slobodne energije. Za poznavanje Gibbsove energije potrebno je poznavati uvijete u kojima se reakcija odvija te entropiju i entalpiju sustava koji su u radu ukratko objašnjeni. Standardne Gibbsove energije imaju konstantne vrijednosti, ali se podaci mogu prilagoditi drugim uvijetima te izračunati promjenu Gibbsove energije pri drugoj temperaturi i tlaku. U radu je objašnjena poveznica između konstante ravnoteţe i Gibbsove energije kao i aktiviteta otopina.This final work describes the free Gibbs energy, what are the characteristics and how it behaves under certain conditions. Free Gibbs energy is named after American physicist and chemist Josiah Willard Gibbs. Gibbs studied chemical reactions and the relationship between reaction systems and the environment. He noticed what free energy is, what are the criteria for spontaneity of reactions and under what conditions the change in free energy can be calculated. In order to calculate Gibbs energy, it is necessary to know the conditions under which the reaction takes place, and the entropy and enthalpy of the systems, which are briefly explained in the paper. The standard Gibbs energies have constant values, but the data can be adjusted to other conditions and the Gibbs energy change can be calculated at a different temperature and pressure. The relationship between the equilibrium constant and Gibbs energy as well as the activity of the solutions is explained in the paper
Mehanochemical synthesis of mixed metal oxides
No full textMehanokemijska sinteza se odnosi na reakcije (najčešće krutina) pod djelovanjem mehaničke energije, kao što je mljevenje u planetarnom kugličnom mlinu. Ova metoda sinteze spojeva je u današnjici sve više zastupljena zbog minimalnih količina otapala tijekom reakcije, čije korištenje je postalo ekološki problematično i energetski zahtjevno u pogledu proizvodnje. Kao polazni reaktanti za ovaj završni rad su uzeti metalni oksidi zbog svojih raznovrsnih svojstava i široke primjene. Odrađene su sinteze uzoraka MH1 (kalcijev hidroksid i cinkov oksid) i MH2 (kalcijev oksid i cinkov oksid) u planetarnom kugličnom mlinu Fritsch Pulverisette Premium 7 line. Dobiveni su spojevi okarakterizirani termogravimetrijskom analizom (TGA) i infracrvenom spektroskopijom (FT-IR). Na temelju dobivenih rezultata pretpostavljeno je dobivanje miješanih metalnih oksida tijekom sinteze u obliku primjesa (nečistoća).Mechanochemical synthesis refers to reactions (mainly solids) under the influence of mechanical energy as is milling in planetary ball mill. These days, this synthesis method is more and more used because of minimum usage of solvents during reaction which, over the time, became environmental issue and energetically demanding in respect of production. For this thesis metal oxides are used as reagents because of their various properties and wide usage. Syntheses of MH1 (calcium hydroxide and zinc oxide are used as reagents) and MH2 (calcium oxide and zinc oxide are used as reagents) were conducted in planetary ball mill Fritsch Pulverisette Premium 7 line. Obtained compounds were characterised with the thermogravimetric analysis (TGA) and infrared spectroscopy (FT-IR). Based on obtained results it is presumed that products are mixture of mixed metal oxides with presence of impurities (byphases)
Oxidation of metals
No full textU ovome radu cilj je bio opisati oksidaciju metala. Kako je tema 'oksidacija metala' široka, rad je podijeljen u tri poglavlja. U prvom dijelu ukratko je pojašnjeno na što se odnosi pojam oksidacijsko - redukcijski procesi, razlika redukcijskog sredstva i oksidacijskog sredstva te što je stupanj oksidacije. Drugi i treći dio rada odnose se na metale. Drugi dio opisuje što su metali, karakteristiku metalne veze i njezine dvije teorije te kako se metali dobivaju. Dok je u trećem dijelu opisana jedna od podjela metala te su obrađeni konkretni primjeri metala. Opisano je kako se i po čemu razlikuju pojedini metali te u kojim oksidacijskim stanjima tvore svoje spojeve.In this paper, the aim was to process metal oxidation. As the topic of 'Oxidation of Metal' is wide, the work is divided into three chapters. In the first chapter, it is briefly clarified with reference the term oxidation- reduction processes, the difference between, the reducing agent and the oxidizing agent, and the degree oxidation. The second and third parts of work refer to metals. The second part describes what metals are, the characteristic of the metal connection and its two theories, and how the metals are obtained. While in the third part there is a description the metal division. Specific examples metal are covered in this section. It is described how and by what they differ, and in which oxidation states they from compounds
Mchanochemical syntesis of metal complexes with Schiffs bases
No full textMehanokemijske sinteze se u današnje vrijeme sve više proučavaju i proširuju zbog toga što omogućavaju nekorištenje otapala (ili pak uporabu minimalne količine otapala), kraće vrijeme sinteze te veće iskorištenje. U ovom diplomskom radu sintetizirani su metalni kompleksi metalnih soli sa Schiffovim bazama metodom visokoenergetskog mljevenja unutar planetarnog kugličnog mlina te su uspoređeni s produktima dobivenim klasičnom sintezom. Dobiveni spojevi okarakterizirani su termogravimatrijskom analizom (TGA), infracrvenom spektroskopijom (FT-IR) i elementnom analizom (CHN). Uz to, mijenjani su promjenjivi parametri kao što su vrijeme sinteze te brzina okretaja kako bi se dobili što točniji uvjeti nastajanja željenih spojeva.Mechanochemical synthesis are being explored and expanded because they allow minimal usability of soluble reactants, or don't use any of it, shorter synthesis time and they are more effective. In this graduate thesis, metal complexes of metal salts with Schiff's bases are synthesized by the method of high-energy grinding within a planetary ball mill and are compared to products of classic synthesis. The obtained compounds are characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and elemental analyses (CHN). On the other hand, variable parameters like reaction time and rotation speed, are changed in order to obtain the most accurate conditions of the desired compounds
Mechanisms og histone modifications
No full textKovalentne modifikacije amino-terminalnih završetaka histona u nukleosomima imaju ključnu ulogu u većini bioloških procesa koji su uključeni u ekspresiju i regulaciju gena. Istraživanja u posljednjih nekoliko godina otkrivaju da se te modifikacije sastoje od acetilacije, metilacije, ubikvitinacije, fosforilacije, sumoilacije itd. Acetilacija histona regulirana je djelovanjem dvaju enzima, histonske acetiltransferaze (HAT) i histonske deacetilaze. Fosforilacija se odvija na serinima, treoninima i tirozinima i to pretežno na N-terminalnom histonskom repu. Metilacija histona javlja se samo na argininima i lizinima. Ubikvitinacija se odnosi na post-translacijsku modifikaciju amino skupine lizinskog ostatka kovalentnim vezanjem jednog ili više ubikvitinskih monomera. Sumoilacija je modifikacija koja je povezana s ubikvitinacijom i uključuje kovaletno vezanje SUMO proteina na lizinske ostatke histona. ADP ribozilacija je post-translacijska modifikacija definirana dodatkom ADP-ribozne komponente na protein koji koristi NAD+ kao supstrat. Posljednjih godina, inhibicija histon deacetilaza (HDAC) pojavila se kao potencijalna strategija za epigenetske promjene povezane s rakom. Nekoliko klasa HDAC inhibitora pokazalo je da imaju snažne i specifične anti-tumorske aktivnosti u predkliničkim istraživanjima.Covalent modifications to the amino - terminal histone ends in nucleosomes have a key role in many biological processes involved in gene expression and regulation. In the recent years, research has shown that these modifications are mainly acetylation, methylation, ubiquitination, phosphorylation, sumoilation etc. Histone acetylation is regulated by activity of two enzymes, histone acetyltransferase (HAT) and histone deacetylase. Phosphorylation acts on serines, threonines and tyrosines and mostly on N-terminal histone tail. Histone methylation occurs only on arginines and lysines. Ubiquitination refers to a post-translational modification of amino group of a lysine residue by covalent bonding of one or more ubiquitin monomers. Sumoilation is a modification which is related to the ubiquitination and includes covalent bonding of SUMO proteins to lysine histone residue. ADP-ribosylation is a post-translational modification defined by adding ADP-ribose component to a protein which uses NAD+ as a substrate. In the recent years, inhibition of the histone deacetylase (HDAC) has surfaced as a potential strategy for epigenetic changes linked to cancer. A few classes of HDAC inhibitors showed that they possess strong and specific anti-tumor activities in preclinical research
Anionic surfactants determination in commercial systms using sensor with functionalized carbon nanotubes
No full textTenzidi su površinski aktivne tvari, tj. tvari koje smanjuju sile koje djeluju između dvije faze. Oni su glavni sastojci deterdženata, no također se rabe i kao omekšivači, emulgatori, sredstva za zaštitu od korozije, za dezinfekciju, u kozmetici i slično. Dijele se na anionske, kationske, neionske i amfolitske. Anionski tenzidi su glavni sastojak sredstava za pranje. Dobivaju se hidrolizom ulja ili masti jakim lužinama. Sastoje se od hidrofobne i hidrofilne skupine. Za određivanje njihovih koncentracija, često se koriste potenciometrijske titracije. Određivanje anionskih tenzida izvedeno je koristeći potenciometrijski senzor s ionskim parom izgrađenim od funkcionaliziranih višestjenčanih ugljikovih nanocjevčica i tetrafenilborata (MWCNT-TPB) kao senzorskim materijalom. Kao titrans je korištena otopina cetilpiridinijeva klorida (CPC), koncentracije 4·( 10^{-3} \) mol/, dok su analiti bile vodene otopine različitih deterdženata. Korištena su 3 komercijalna proizvoda s različitim postotkom anionskih tenzida: <5%, 5-15% i 15-30%. Kao standardni dodatak, koristio se natrijev dodecilsulfat (NaDDS) koncentracije 4·( 10^{-3} \) mol/. Rezultati su uspoređeni s rezultatima dobivenim titracijom u dvije faze.Surfactants or surface active agents are substances that reduce forces between two phases. They are the main constituents of detergents, but they are also used as softeners, emulsifiers, corrosion protection agents, for disinfection, in cosmetics and others. They are divided into anionic, cationic, nonionic and amphoteric. Anionic surfactants are a major constituent of detergents. They are obtained by hydrolysis of oil or grease with strong alkalis. They consist of a hydrophobic and a hydrophilic group. Potentiometric titrations are often used to determine their concentrations. Determination of anionic surfactants was performed using a potentiometric sensor with ion pair consisted of functionalized multiwalled carbon nanotubes and tetraphenylborate (MWCNT-TPB) as the sensing material. The cetylpyridinium chloride (CPC), at concentration of 4 · mol/ was used as titrant, while the analytes were aqueous solutions of various detergents. Three commercial products with different percentage of anionic surfactants: <5%, 5-15% and 15-30%, were used. Sodium dodecyl sulfate (NaDDS) at concentration of 4 · mol/ was used as a standard additon. The results were compared with those obtained using two-phase titration
Assessment of selected rare earth elements in urine (ICP-MS)
No full textElementi rijetkih zemalja imaju brojne primjene u industriji zbog kojih je sve učestaliji izravan doticaj čovjeka s njihovim spojevima. Potencijalne dugoročne posljedice i akumulacija u ljudskom organizmu nisu detaljno istražene. Za ovaj rad odabrano je 12 elemenata: lantan, (La), cerij, (Ce), praseodimij, (Pr), neodimij, (Nd), samarij, (Sm), europij, (Eu) gadolinij, (Gd), disprozij, (Dy), holmij, (Ho), erbij, (Er), tulij, (Tm), iterbij, (Yb) te je metodom induktivno spregnuta plazma-masene spektroskopije (ICP-MS) određena njihova koncentracija u urinu ispitanika sa područja istočne Hrvatske, odabrane su lokacije: Dalj, Vladislavci, Osijek, Našice i Čepin. Obrada podataka pokazala je da su se vrijednosti medijana koncentracija Svih analiziranih elemenata na svim istraživanim lokacijama nalazile ispod granice detekcije mjernog instrumenta.Rare earth elements are metals mostly contained in monazite ores. Their properties and cheapness make them highly usable in numerous industries. Toxicity and long term effect on human health need further research. In this study concentrations of twelve rare earth elements, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy), Ho, Er, Tm, Yb from samples of urine are determined by using inductively coupled plasma mass spectrometry(ICP-MS) method. Samples were collected in eastern Croatia; in Osijek, Našice, Dalj, Vladislavci and Čepin. Median values for twelve elements from five sample locations are below detection level
Entalphy
No full textU ovom završnom radu opisana je entalpija. Entalpija je važna termodinamička funkcija koja je jednaka toplinskoj energiji koja je prinešena sustavu. U sustavima koji slobodno mijenjaju svoj volumen, promjena unutarnje energije nije jednaka energiji koja se prinese sustavu kao toplina jer se dio toplinske energije troši na ekspanzijski rad. Entalpija je funkcija stanja jer je definirana promjenom unutrarnje energije, tlakom i volumenom koje su također funkcije stanja. Promjena entalpije je mjerljiva veličina koja se može odrediti eksperimentalno ili računski. Eksperimentalno se određuje kalorimetrijom, a ako eksperimentalno nije moguće odrediti entalpiju koristi se Hessov zakon. Pojam toplinski kapacitet pomaže pri povezivanju promjene entalpije sa temperaturom.This final paper describes the enthalpy. Enthalpy is an important thermodynamic function that is equal to the thermal energy suplied to the system. In systems which freely change their volume, the change in internal energy is not equal to the energy suplied to the system as heat since one part of that energy is used for expansion work. The enthalpy is a state function because it is defined with change in internal energy, pressure and volume, which are also state functions. Change of enthalpy is a measurable quantity that can be determined experimentally or computationally. It is determined experimentally by using calorimetry, and if it is not experimentally possible to determine the enthalpy, Hess law is used. The term heat capacity is used to associate enthalpy change with temperature
Synthesis and characterization of Schiff bases derived from aminopyridine
No full textSchiffove baze su vrsta organskih spojeva koje sadrže C=N dvostruku vezu te se sintetiziraju reakcijom kondenzacije primarnih amina i aldehida. Prilikom sinteze Schiffovih baza, treba obratiti pažnju na dva uvjeta u kojima se reakcija odvija. Katalizator koji se koristi pri sintezi treba biti umjereno kiseo (pH 3-5) kako bi došlo do eliminacije vode i stvaranja C=N veze. Kao reaktanti u sintezi, mogu se koristiti aminopiridini i dialdehidi u blago kiseloj sredini (HCl ili CH3COOH) uz etanol kao otapalo. Aminopiridini su spojevi koji se sastoje od piridinskog prstena na koji je vezana amino skupina -NH2 na različita mjesta. Postoje tri vrste položajnih izomera, a to su 2-aminopiridin, 3-aminopiridin i 4-aminopiridin. Upotrebom kiselog medija dolazi do deprotoniranja dušika aminoskupine koji reagira sa karbonilnom skupinom aldehida i nastaje C=N veza. Dialdehidi su spojevi koji sadrže dvije karbonilne skupine te reakcijom s aminopiridinima tvore C=N vezu na obje skupine. Mogu se sintetizirati iz aldehida i halogenoalkana pri visokoj temperaturi uz dimetilformamid kao otapalo. U ovom završnom radu sintetizirano je trinaest spojeva metodama otopinske kemije. Nastali produkti su karakterizirani FT-IR spektroskopijom te im je izvagana masa, a sintetiziranim dialdehidima osim mase, određena je i temperatura tališta.Schiff bases are a organic compounds that contain C=N bond and can be synthetised by condesation reaction of primary amines and aldehydes. During the Schiff bases synthesis, two factors are of importance and should be considered. The catalyst that is used in a formation of Schiff bases has to be mildly acidic (pH 3-5) to eliminate water molecule in order to form C=N bond in a compound. As a synthesis reactants, aminopyridines and dialdehydes, can be used in a mildly acidic conditions (HCl or CH3COOH) with ethanol as a solvent. Aminopyridines are compounds that contain pyridine ring that has amino group -NH2 attached on different carbon atom. There are three types of positional isomers of aminopyridines: 2-aminopyiridine, 3-aminopyridine, 4-aminopyridine. Under acidic conditions, nitrogen atom of amino group is deprotonated and reacts with a carbonyl aldehyde group and forms C=N bond. Dialdehyds are compounds that contain two carbonyl groups and by reacting with aminopyridines form C=N bond on both sides. They can be prepared by aldehydes and halogenalkanes on high temperature and dimethylformamide as a solvent. In this final paper, thirteen compounds were synthetised using methods of solution chemistry. Synthetised products were characterized by FT-IR spectroscopy, their mass has been weighed down and the melting point was determined for dialdehydes
Salicine and its derivatives
No full textSalicin je prvi fenolni glukozid pronađen u prirodi, a oralnom primjenom metabolizira u farmakološki aktivni oblik salicilnu kiselinu. Postoji mnogo derivata salicilne kiseline, od kojih je jedan najpoznatiji i najviše korišten lijek, acetilsalicilna kiselina ili Aspirin®. Aspirin je lijek koji ima svojstvo antipiretika i antikoagulanta, a djeluje tako što inhibira aktivnost enzima kao ciklooksigenaze koji dovodi do stvaranja prostaglandina, tvari odgovorne za upalu i bol. Najpoznatija metoda sinteze acetilsalicilne kiseline je esterifikacija salicilne kiseline acetanhidridom uz fosfatnu ili sumpornu kiselinu. Cilj završnog rada bio je ispitati mogućnost sinteze acetilsalicilne kiseline reakcijom esterifikacije salicilne kiseline acetanhidridom konvencionalnom metodom, ali uz uporabu eutektičkih otapala na bazi kolin-klorida (ChCl) za koja se može pretpostaviti katalitička uloga u reakciji esterifikacije. Rezultati eksperimentalnog rada pokazali su da se eutektičko otapalo ChCl: levulinska kiselina i ChCl: limunska kiselina ne mogu koristiti kao katalizator u sintezi acetilsalicilne kiseline. Međutim, uz uporabu eutektičkog otapala ChCl : urea dobivena je acetilsalicilna kiselina pri čemu je po prvi puta potvrđena mogućnost primjene eutektičkih otapala u sintezi acetilsalicilne kiseline.Salicin is the first phenolic glucoside found in nature and after oral use it is metabolized to a pharmacologically active form, salicylic acid. There are many salicylic acid derivatives, one of which is the most commonly used drug, acetylsalicylic acid or aspirin. Aspirin is a medicine that has antipyretic and anticoagulant properties and acts by inhibiting activity of the enzyme cyclooxygenase which is responsible for the production of prostaglandins, substances responsible for inflammation and pain. The most known method of aspirin synthesis is esterification of salicylic acid with acetic anhydride with phosphoric or sulfuric acid. The aim of final thesis was to investigate the possibility of aspirin synthesis by conventional method, but with the use of choline chloride (ChCl) eutectic solvents for which a catalytic role in the esterification reaction can be assumed. The results of the experimental work showed that the eutectic solvents ChCl: levulinic acid and ChCl: citric acid can't be used as catalyst for the acetylsalicylic acid synthesis. However, with the use of eutectic solvent ChCl: urea, acetylsalicylic acid was obtained and for the first time the possibility of using eutectic solvent in the acetylsalicylic acid synthesis was confirmed