Vpliv van der Waalsovih sil na tvorbo asociiranih molekul

diplomsko delo univerzitetnega študijskega programa I. stopnje

Bernarda Kuster (Author), Aljana Petek (Mentor), Majda Krajnc (Co-mentor)

Abstract

Namen diplomske naloge je preučiti vpliv van der Waalsovih sil na tvorbo asociiranih molekul. V ta namen smo izbrali površinsko aktivne snovi, ki imajo amfifilne lastnosti in vplivajo na povšinske in medfazne napetosti ter pri določeni koncentraciji, imenovani kritična micelna koncentracija (CMC), tvorijo molekulske skupke, ki jim pravimo micele. Kritično micelno koncentracijo smo določili trem površinsko aktivnim snovem: heksadeciltrimetilamonijevemu bromidu, tetradeciltrimetilamonijevemu bromidu in n dodeciltrimetilamonijevemu bromidu. Eksperimente smo izvajali pri temperaturah 25 °C, 30 °C in 35 °C s klasično konduktometrično metodo. Na osnovi rezultatov smo analizirali vpliv van der Waalsovih sil na proces asociacije molekul v micele. Za izbrano temperaturno območje smo ugotovili, da vrednosti kritične micelne koncentracije rastejo s povišanjem temperature in da se z višanjem števila C atomov v molekuli površinsko aktivne snovi kritične micelne koncentracije znižujejo. Po izračunu stopnje ionizacije micele α, stopnje vezave protiiona β in standardne Gibbsove proste energije pri micelizaciji 〖∆G〗_mic^°, smo ugotovili, da so vrednosti standardne Gibbsove proste energije pri micelizaciji v vseh primerih negativne in s podaljševanjem alkilne verige v molekuli padajo, kar si razlagamo kot krepitev privlačnih van der Waalsovih sil, ki posledično povzročijo nastanek micele pri nižji vrednosti kritične micelne koncentracije.

Keywords

van der Waalsove sile;specifična prevodnost raztopin;površinsko aktivna snov;kritična micelna koncentracija;heksadecilitrimetilamonijev bromid;tetradeciltrimetilamonijev bromid;n-dodeciltrimetilamonijev bromid;

Data

Language:	Slovenian
Year of publishing:	2014
Typology:	2.11 - Undergraduate Thesis
Organization:	UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher:	[B. Kuster]
UDC:	544.35.03:537.311(043.2)
COBISS:	18226198
Views:	1450
Downloads:	103
Average score:	0 (0 votes)
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Other data

Secondary language:	English
Secondary title:	THE INFLUENCE OF INTERMOLECULAR VAN DER WAALS FORCES ON THE FORMATION OF ASSOCIATED MOLECULES
Secondary abstract:	The aim of the diploma thesis was to investigate the influence of van der Waals forces on formation of the associated molecules. For this purpose we chose surface active agents, which have amphiphilic properties and they affect on surface and interface tensions and on the certain concentration, called critical micelle concentration (CMC), they form molecular assemblies, known as micelles. We determined critical micelle concentration to three surfactants: hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and n-dodecyltrimethylammonium bromide. We executed the experiment at temperatures 25 °C, 30 °C and 35 °C with clasic conductometry method. On the basis of the results, we analysed the influence of van der Waals forces on the process of association of molecules to micelles. For chosen temperature range, we found out, that values of critical micelle concentration increase with increasing temperature and with the extension of the number of C atoms in molecule of surfactant critical micelle concentration decreases. According to calculation of ionization degree α, degree of binding counterion β and standard Gibbs energy of micellization 〖∆G〗_mic^°, we found out, that values of standard Gibbs energy of micellization are in all cases negative and with extending alkyl chain in molecule, decrease, what we explain as enhancement of attractive van der Waals forces, which consequentially cause formation of micelle at lower value of critical micelle concentration.
Secondary keywords:	van der Waals forces;conductivity;critical micelle concentration;hexadecyltrimethylammonium bromide;tetradecyltrimethylammonium bromide;n-dodecyltrimthylammonium bromide;
URN:	URN:SI:UM:
Type (COBISS):	Bachelor thesis/paper
Thesis comment:	Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages:	XIII, 66 str.
ID:	8730039