Razvoj metodologije za izravno izotermno kalorimetrijsko određivanje reakcijskih entalpija procesa u čvrstom stanju

master's thesis

• Title (english): Methodology development for direct isothermic calorimetric determination of reaction enthalpies of processes in solid state
• Author: Robert Šplajt
• Mentor: Nikola Bregović (mentor)
• Committee member: Dominik Cinčić (predsjednik povjerenstva)
• Committee member: Snežana Miljanić (član povjerenstva)
• Committee member: Nikola Bregović (član povjerenstva)
• Committee member: Josip Požar (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Chemistry); Zagreb
• Defense date and country: 2023-02-24, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry

Abstract

U ovom radu istražene su mogućnosti korištenja Calvetovog kalorimetra za izravno izotermno
kalorimetrijsko određivanje reakcijskih entalpija procesa u čvrstom stanju.
Reakcije karboksilnih kiselina i 4-N,N-dimetilaminopiridina provedene su uz značajan
suvišak kiselina te su potpomognute dodatkom male količine metanola pri čemu dolazi do
nastajanja kokristala soli pridinijevog karboksilata s karboksilnom kiselinom. Određene su
odgovarajuće reakcijske entalpije, a izmjerene su i reakcije stvaranja kokristala iz prethodno
dobivenih soli. Dobivene vrijednosti reakcijskih entalpija i reaktivnost istraživanih sustava
diskutirani su s obzirom na strukturu korištenih kiselina, njihove kiselosti i mogućnosti
ostvarivanja vodikovih veza.
Neposrednom izotermnom kalorimetrijom određene su i reakcijske entalpije taljenja
ekvimolarne smjese benzofenona i difenilamina pri 25 °C te nastajanja kokristala iz
metastabilne tekućine uslijed dodatka klice kokristala.
Produkti svih istraženih reakcija identificirani su na temelju difraktograma praškastih
uzoraka. Reakcijske entalpije izmjerene neposredno izotermnom kalorimetrijom uspoređene su
s onima određenim na temelju termodinamičkih ciklusa. U tu svrhu kalorimetrijski su određene
entalpije otapanja krutih reaktanata i produkata te entalpije odgovarajućih reakcija u otopini.
Rezultati dobiveni pomoću obje metode vrlo dobro se slažu čime je potvrđena pouzdanost
razvijene metode izravnog izotermnog kalorimetrijskog određivanja entalpija reakcija u
čvrstom stanju.

Abstract (english)

The potential of using a Calvet calorimeter for direct determination of reaction enthalpies for
processes between solid reactants at isothermal conditions was investigated in this work.
The reactions of carboxylic acids with 4-N,N-dimethylaminopyridine were carried out
using a significant excess of the acid and assisted by addition of methanol. Co-crystals of
protonated carboxylic acids with the corresponding salts were the favoured products at the
conditions used. The reaction enthalpies related to formation of the co-crystals from either free
base or previously prepared salts were determined. The obtained results were discussed with
respect to the molecular structures and pKa values of the studied acids and their potential to
form hydrogen bonds.
The enthalpy changes related to the melting od benzophenon and diphenylamine mixed
in equimolar ratio and subsequent co-crystal formation from the metastable melt by addition of
a crystalline seed were measured.
The reaction products were identified by powder X-ray diffraction which also enabled
the determination of reaction extent. The results of direct calorimetric measurements were
validated by correlation with those based on Hess's law. This yielded an excellent data
agreement, confirming the reliability of the herein developed methodology.

• Keywords: reakcije u čvrstom stanju; izotermna kalorimetrija; kokristali; prijenos protona; reakcijska entalpija; termodinamički ciklusi
• Keywords (english): solid-state reactions; isothermal calorimetry; co-crystals; proton transfer; reaction enthalpy; thermodynamic cycles
• Language: croatian
• URN:NBN: urn:nbn:hr:217:076275
• Project: Number: IP-2019-04-9560; Title: Koordinacijske reakcije makrocikličkih liganada u otopini; Title: Coordination Reactions of Macrocyclic Ligands in Solution; Acronym: MacroSol; Leader: Vladislav Tomišić; Jurisdiction: Croatia; Funder: HRZZ; Funding stream: IP
• Study programme: Title: Graduate university studies in chemistry; specializations in: Research programme; Course: Research programme; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra kemije (magistar/magistra kemije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access; Embargo expiration date: 2023-08-24
• Created on: 2023-04-03 12:11:32