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Flow Accelerated Corrosion Experience at Comanche Peak Steam Electric Station
Flow accelerated corrosion (FAC) is a major concern in the power industry as it causes thinning of the pipes by the dissolution of the passive oxide layer formed on the pipe surface. Present research deals with comparing the protection offered by the magnetite (Fe3O4) versus maghemite (γ-Fe2O3) phases thickness loss measurements. Fourier transform infrared spectroscopy (FTIR) is used in distinguishing these two elusive phases of iron oxides. Representative pipes are collected from high pressure steam extraction line of the secondary cycle of unit 2 of Comanche Peak Steam Electric Station (CPSES). Environmental scanning electron microscopy (ESEM) is used for morphological analysis. FTIR and X-ray diffraction (XRD) are used for phase analysis. Morphological analysis showed the presence of porous oxide surfaces with octahedral crystals, scallops and "chimney" like vents. FTIR revealed the predominance of maghemite at the most of the pipe sections. Results of thickness measurements indicate severe thickness loss at the bend areas (extrados) of the pipes.
Date:
May 2008
Creator:
Nakka, Ravi Kumar
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
An Exploration of the Relationship between Worry and Other Verbal Phenomena
This study hypothesized a direct relationship among three verbal phenomena: derived relational responding, verbal intelligence, and worry. It also hypothesized that experiential avoidance would mediate the relationship between derived relational responding and worry. Overall, results from this study failed to support a relationship between worry and the other two verbal phenomena, however, results did support a relationship between derived relational responding and verbal intelligence. Additionally, results indicated a significant relationship between experiential avoidance and worry. Future research should clarify the relationship among the three primary variables of interest, improve measurement of these variables, be more sensitive to external validity, and promote the study of acceptance-based treatments that target experiential avoidance.
Date:
May 2008
Creator:
O'Brien, Karen M.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Exploratory Study of Animal Assisted Therapy Interventions Used by Mental Health Professionals
The purpose of this study was to explore the various animal assisted interventions mental health professionals incorporate in the therapeutic treatment process, as well as the various therapeutic purposes intended with each technique. Participants were recruited from animal assisted therapy related databases. Participants included professionals who practiced in the mental health field. Thirty one participants qualified for the study. A survey was developed based on information found reviewing literature related to animal assisted therapy. Nineteen animal assisted therapy techniques and ten therapeutic intentions were identified from a review of the literature. Participants were asked to rate on a Likert scale how often they incorporated each technique in their treatment process. Additionally, participants were asked to identify which therapeutic purposes they intended with each technique. Results indicated participants incorporated a variety of animal assisted techniques for various therapeutic intentions. Results indicated seven animal assisted techniques were incorporated by more than 50% of the participants. Building rapport in the therapeutic relationship was the most common therapeutic intention reported with a variety of animal assisted techniques.
Date:
May 2008
Creator:
O'Callaghan, Dana M.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Educating Young Children with Autism in Inclusive Classrooms in Thailand
This study investigated what constitutes a teaching curriculum for students with autism in inclusive classrooms in Thailand. The researcher employed 3 qualitative methods: semi-structured interviews, document analysis of curricula and lesson plans, and nonparticipant observations. Six schools were selected as the sites. Participants for interview included 6 principals and 24 teachers. The researcher observed one inclusive classroom for each of the 6 selected schools. The study concentrated on 3 questions: (a) What contributes to appropriate instructional curricula to promote teaching of students with autism in inclusive classrooms in Thailand? (b) What teaching strategies improve the achievement and learning skills of students with autism in inclusive classrooms in Thailand? (c) What are the problems of curricula for teaching students with autism in inclusive classroom in Thailand? Key findings for the research questions were as follows: Common features of effective curricula for teaching students with autism in inclusive classrooms include opportunities, health care, specialized curriculum, students' individual needs and abilities, guidelines of teaching, teacher training and supervision, transition plan, parent involvement, tools/classroom environment, and students' class assignments. The teaching strategies include varying the teaching format (large group, small group, and one-on-one), teaching functional communication (giving direction, close-ended questions or open-ended questions), reinforce …
Date:
May 2008
Creator:
Onbun-uea, Angkhana
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Preferences among student counselors regarding informed consent practices within counselor education.
The purpose of this study was to investigate student preferences for content, timing, and method of informed consent within counselor education programs. Participants included 115 students enrolled in counseling internship courses at six counseling programs accredited by the Council for Accreditation of Counseling and Related Educational Programs (CACREP). Participants completed the Informed Consent Preferences Questionnaire (ICPQ), an instrument designed specifically for this study through systematic instrumentation development. Descriptive statistics highlighted participants' moderate to high ratings of perceived importance for an array of suggested content pieces for student informed consent. Participants varied among themselves and between items in relation to preferred timing of informed consent, and they consistently reported a desire for student informed consent to be facilitated through a combination of both oral and written methods. Results of exploratory factor analysis revealed a simple eight-factor structure within the ICPQ and suggested strong internal reliability. Correlations for participant scale scores for the eight factors revealed a variety of small to medium correlations. Results from t-test and one-way analysis of variances (ANOVA) indicated that participant preferences did not vary according to demographic variables. Finally, participants' qualitative responses revealed high levels of support for student informed consent. Findings of this study may aid …
Date:
May 2008
Creator:
Pease-Carter, Cheyenne
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Performance Implications of Multi-Channel Strategic Decisions by Incumbent Retailers: The Role of Order of Entry and Degree of Inter-Channel Coordination
The rapidly intensifying adoption of the Internet channel for marketing and sales by incumbent bricks-and-mortar retailers underscores the importance of assessing the impact of the online channel strategies on firm performance in the dynamic competitive environment. At the time when store-based retailers increasingly dominate online sales the questions of when and how an incumbent retailer should adopt an online channel to achieve and sustain a competitive advantage are of utmost interest for both marketing scholars and practitioners. This dissertation investigates the role of two strategic decisions in affecting firm performance: (a) the order of adopting an online channel by incumbent retailers and (b) the degree of coordination between store and online sales channels. The resource-based view and the dynamic capabilities approach are used as theoretical foundations for the study. Following resource-based logic and applying a contingency perspective, this research proposes that firm-specific resource endowments determine the success of the order of online entry strategy for incumbent retailers. This dissertation utilizes the dynamic capabilities approach to propose that the strategy of inter-channel channel coordination leads to higher performance when core, unique dynamic capabilities pertaining to e-commerce are developed in-house, as opposed to being outsourced. By posing and answering the research questions …
Date:
May 2008
Creator:
Pentina, Iryna
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Expanded Perceptions of Identity in Benjamin Britten's Nocturne, Op. 60
A concentrated reading of Benjamin Britten's Nocturne through details of the composer's biography can lead to new perspectives on the composer's identity. The method employed broadens current understandings of Britten's personality and its relationship to the music. After creating a context for this kind of work within Britten scholarship, each chapter explores a specific aspect of Britten's identity through the individual songs of the Nocturne. Chapter 2 focuses on how Britten used genres in a pastoral style to create his own British identity. Chapter 3 concentrates on the complex relationship between Britten's homosexuality and his pacifism. Chapter 4 aims to achieve a deeper understanding of Britten's idealization of innocence. The various aspects of Britten's personality are related to one another in the Conclusion.
Date:
May 2008
Creator:
Perkins, Anna Grace
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Networked generation youth's information seeking process: An examination of cognitive, affective and physical behaviors and problem solving techniques.
This study investigated the information seeking process of the networked generation youth. Specifically, I examined the cognitive, affective, and physical information seeking behaviors and problem solving techniques adolescent student users of the networked environment utilize to solve information needs. Grounded in the theoretical context of the information seeking process in the networked environment, the research extended the user-centered approach to modeling the information seeking process of networked generation youth. A mixed model research design was used to address the research questions. Phase 1 used an online questionnaire to solicit information from 125 students in Grades 7-12 regarding their understanding and use of networked environments, information seeking skills, and problem solving techniques. Phase 2 observed 12 students, two from each grade level, to gain an understanding into the information seeking process of networked generation youth. Participants completed information seeking scenarios of varying levels of complexity. As the participants completed the scenario, they engaged in talk-aloud verbal protocol to describe and explain their behaviors and techniques as they advanced through their information seeking process. Semi-structured interviews were conducted which provided an opportunity for the participants to clarify their information seeking experience. A profile of students' networked environment knowledge and use in relationship …
Date:
May 2008
Creator:
Peterson, Janet Walker
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Mozartean Gesture and Rhetoric in Hummel's Concerto for Trumpet
Hummel's Concerto for Trumpet (Concerto a Tromba principale) is overtly operatic and is stylistically reminiscent of Mozart's Don Giovanni. Using the methodology of Leonard Ratner and Wye J. Allanbrook, it is possible to explore gesture and rhetoric in Hummel's Concerto for Trumpet and Mozart's Don Giovanni, and achieve a deeper understanding of the stylistic similarities shared between the two works. In the third movement, dance is the most significant link to Don Giovanni. In the second movement, Hummel alternates between the emotions of Donna Anna and Don Ottavio as they appear in act 1, scene 13. The first movement makes extensive use of contrasting topics identified with buffa and seria characters to advance the musical narrative. Comparing Hummel's concerto and Mozart's opera is a hermeneutical approach that illuminates several performance practice implications. Knowing the expressive similarities and rhetorical strategies common to both works clarifies several issues, such as tempo, ornamentation, and above all, expression. Though Mozart's Don Giovanni and Hummel's Concerto for Trumpet are unequal in significance, it would be valuable to any interpretation of Hummel's concerto if the performer and audience acknowledge that the work is rhetorically and stylistically similar to Mozart's Don Giovanni.
Date:
May 2008
Creator:
Phillips, Edward
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
An Analysis of Form and Tonality in Arnold Cooke's Sonata for Oboe and Piano (1957)
Arnold Cooke composed many works for oboe including two sonatas, a concerto and several pieces for chamber ensembles; however, his works are rarely performed. Through the analysis of form and tonality in his first oboe sonata, Cooke's musical style and influences become apparent. His musical style was primarily influenced by his teacher, Paul Hindemith, and can be characterized by traditional forms with the contemporary use of quartal harmonies and a variety of tertian sonorities. Cooke wrote music that is accessible for performers and audience members, and one way he achieved this accessibility is through the repetition of melodic ideas. In addition to exact melodic repetition, he also unified his works through fugue-like passages and sequences. Although he lived during a time of experimentation by many composers, Cooke maintained conservative elements in his music that he learned through his studies at Cambridge and through his studies with Hindemith. His first oboe sonata is tonal although he varied modes and used chromatic harmonies throughout. Cooke's clear writing and unique sound in his Sonata for Oboe and Piano (1957) provide oboists a solo piece for the repertoire that demonstrates a modern approach to the traditional style of composition.
Date:
May 2008
Creator:
Polk, Kristin Marie
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Localized Radial Solutions for Nonlinear p-Laplacian Equation in RN
We establish the existence of radial solutions to the p-Laplacian equation ∆p u + f(u)=0 in RN, where f behaves like |u|q-1 u when u is large and f(u) < 0 for small positive u. We show that for each nonnegative integer n, there is a localized solution u which has exactly n zeros. Also, we look for radial solutions of a superlinear Dirichlet problem in a ball. We show that for each nonnegative integer n, there is a solution u which has exactly n zeros. Here we give an alternate proof to that which was given by Castro and Kurepa.
Date:
May 2008
Creator:
Pudipeddi, Sridevi
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Career and Legacy of Hornist Joseph Eger: His Solo Career, Recordings, and Arrangements
This study documents the career of Joseph Eger (b. 1920), who had a short but remarkable playing career in the 1940s, 1950s and early 1960s. Eger toured the United States and Britain as a soloist with his own group, even trading tours with the legendary British hornist, Dennis Brain. He recorded a brilliant solo album, transcribed or arranged several solos for horn, and premiered compositions now standard in the horn repertoire. He served as Principal Horn of the New York Philharmonic, Los Angeles Philharmonic, and the National Symphony. Despite his illustrious career as a hornist, many horn players today do not recognize his name. While Eger was a renowned horn soloist in the middle of the twentieth century, he all but disappeared as a hornist, refocused his career, and reemerged as a conductor, social activist, and author. This dissertation seeks to be the long-overdue comprehensive documentation of Eger's career as the first American horn soloist and his contributions to the world of horn playing. First, a biography of Eger is presented, focusing especially on his education and career as an orchestral player, soloist, and recording artist, including its intersections with the lives of many prominent musicians and personalities of the …
Date:
May 2008
Creator:
Pritchett, Kathleen S.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
A weak link in the chain: The Joint Chiefs of Staff and the Truman-MacArthur controversy during the Korean War.
This work examines the actions of the Joint Chiefs of Staff during the first year of the Korean War. Officially created in 1947, the Joint Chiefs saw their first true test as an institution during the conflict. At various times, the members of the JCS failed to issue direct orders to their subordinate, resulting in a divide between the wishes of President Truman and General MacArthur over the conduct of the war. By analyzing the interaction between the Joint Chiefs and General Douglas MacArthur, the flaws of both the individual Chiefs as well as the organization as a whole become apparent. The tactical and strategic decisions faced by the JCS are framed within the three main stages of the Korean War.
Date:
May 2008
Creator:
Sager, John
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Actions and Operational Thinking of Generals Stratemeyer and Partridge during the Korean War: Adjusting to Political Restrictions of Air Campaigns
Airpower played an important supporting role in the Korean War, and as General of the Army Douglas MacArthur pursued victory in the war and President Harry S Truman's objectives altered throughout the first year of the conflict, tension arose between the two men. One issue in these frictions was the restriction of airpower. Not only MacArthur, but also his admiring subordinate Lieutenant General George E. Stratemeyer commanding the Far East Air Forces, and Fifth Air Force commander Major General Earle E. Partridge opposed the restrictions which had been imposed on airmen from the outset of the conflict. Stratemeyer did so partly because of his loyalty to MacArthur, who wanted latitude in coping with the situation in the field and defeating the Communist enemy. Partridge did so because he thought they endangered his personnel and limited the effectiveness of airpower in the war. These commanders had a fundamentally different opinion from Washington regarding the likelihood of overt Soviet intervention in the war, and because they did not think the Korean War would become a world war, they were more willing than Washington to prosecute the war more aggressively. MacArthur's conflict ended with his removal in April 1951, and Stratemeyer (who suffered …
Date:
May 2008
Creator:
Sambaluk, Nicholas Michael
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
A Critique of Etudes and Method Books for Advanced Euphoniumists: Status Quo and Future Recommendations
Etudes and method books played had an important role in teaching technique and musicality for all musicians. Euphonium players have been using pedagogical materials originally written for other brass instruments such as trumpet, cornet, and trombone. Those materials have been very effective in helping euphoniumists learn skills to play idiomatic nineteenth and early twentieth century repertoire. In recent years, many solo pieces for euphonium demanding advanced techniques have been composed. The difficulty of these solo works for euphonium has increased dramatically in the second half of the twentieth century. Traditional etudes and method books do not cover all the necessary techniques to play this modern repertoire. In the last two decades, many collections of etudes have been written specifically for euphonium, and several of them are technically challenging and aimed at advanced euphoniumists. This trend can be seen in the United States, France and England. In this paper, traditional standard pedagogical materials currently used by euphoniumists will be evaluated. Recent publications of pedagogical materials written exclusively for euphonium after 1990 will be introduced, and effective uses of old and new pedagogical materials for current euphonium players will be presented. An annotated list of the latest etudes composed exclusively for euphonium …
Date:
May 2008
Creator:
Saito, Mitsuru
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Syncretisms for wind quintet and percussion: A study in combining organizational principles from Southeast Asian music with western stylistic elements.
Syncretisms is an original composition scored for flute, oboe, clarinet, horn, bassoon, and marimba (2-mallet minimum, 4 recommended) with an optional percussion part requiring glockenspiel and chimes, and has an approximate duration of 6 min. 45. sec. The composition combines modern western tuning, timbre, and harmonic language with organizational principles identified in music from Southeast Asia (including music from cultures found in Thailand, Cambodia, Malaysia, and Indonesia). The accompanying paper describes each of these organizational principles, drawing on the work of scholars who have performed fieldwork, and describes the way in which each principle was employed in Syncretisms. The conclusion speculates on a method for comparing musical organizational systems cross-culturally.
Date:
May 2008
Creator:
Seymour, John
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
School based child parent relationship therapy (CPRT) with low income Black American parents: Effects on children's behaviors and parent-child relationship stress, a pilot study.
This study examined the effectiveness of training low income Black American parents in child parent relationship therapy (CPRT). In response to the cultural values and challenges faced by low income Black American parents, the CPRT manual was adapted slightly for use with parents for this study. In this quasi-experimental design, 14 parents were assigned to the experimental group and 13 parents were assigned to the no treatment control group. Six hypotheses were analyzed. Different analyses were conducted based on the hypotheses. A two-factor repeated measures analysis of variance and analysis of covariance were conducted to determine if the CPRT treatment and the no treatment control group performed differently across time according to pretest and posttest results of the Child Behavior Checklist - Parent Version (CBCL) and the Parenting Stress Index (PSI). Additionally, partial η2 was calculated to determine practical significance. Five hypotheses were retained at the .025 level of significance. Findings indicated that parents who participated in the CPRT training reported a statistically significant decrease in parent-child relationship stress. Specifically, parents assigned to the experimental group demonstrated a statistically significant decrease in Child Domain (p < .001), Parent Domain (p < .001), and Total Stress (p < .001) of the …
Date:
May 2008
Creator:
Sheely, Angela
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Relationships Between Perceived Parenting Style, Academic Self-Efficacy and College Adjustment of Freshman Engineering Students
This study examined the relationships between perceived parenting styles, academic self-efficacy, and college adjustment among a sample of 31 freshman engineering students. Through the administration of self-report surveys and chi-square analyses, strong academic self-efficacy was demonstrated in students who reported authoritative maternal parenting. These findings support previous research on the relationship between academic self-efficacy and parenting styles. Implications were drawn for parents and future research.
Date:
May 2008
Creator:
Shaw, Nancy Elaine
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Advanced Technology for Source Drain Resistance Reduction in Nanoscale FinFETs
Dual gate MOSFET structures such as FinFETs are widely regarded as the most promising option for continued scaling of silicon based transistors after 2010. This work examines key process modules that enable reduction of both device area and fin width beyond requirements for the 16nm node. Because aggressively scaled FinFET structures suffer significantly degraded device performance due to large source/drain series resistance (RS/D), several methods to mitigate RS/D such as maximizing contact area, silicide engineering, and epitaxially raised S/D have been evaluated.
Date:
May 2008
Creator:
Smith, Casey Eben
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Libertines Real and Fictional in Rochester, Shadwell, Wycherley, and Boswell
Libertines Real and Fictional in Rochester, Shadwell, Wycherley, and Boswell examines the Restoration and eighteenth-century libertine figure as it appears in John Wilmot, Second Earl of Rochester's Satyr against Mankind, "The Maim'd Debauchee," and "Upon His Drinking a Bowl," Thomas Shadwell's The Libertine, William Wycherley's The Country Wife, and James Boswell's London Journal, 1762-1763. I argue that the limitations and self-contradictions of standard definitions of libertinism and the ways in which libertine protagonists and libertinism in general function as critiques of libertinism. Moreover, libertine protagonists and poetic personae reinterpret libertinism to accommodate their personal agendas and in doing so, satirize the idea of libertinism itself and identify the problematization of "libertinism" as a category of gender and social identity. That is, these libertines misinterpret-often deliberately-Hobbes to justify their opposition and refusal to obey social institutions-e.g., eventually marrying and engaging in a monogamous relationship with one's wife-as well as their endorsement of obedience to nature or sense, which can include embracing a libertine lifestyle in which one engages in sexual encounters with multiple partners, refuses marriage, and questions the existence of God or at least distrusts any sort of organized religion. Since any attempts to define the word "libertinism"-or at least …
Date:
May 2008
Creator:
Smith, Victoria
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Orientation, Microstructure and Pile-Up Effects on Nanoindentation Measurements of FCC and BCC Metals
This study deals with crystal orientation effect along with the effects of microstructure on the pile-ups which affect the nanoindentation measurements. Two metal classes, face centered cubic (FCC) and body centered cubic (BCC, are dealt with in the present study. The objective of this study was to find out the degree of inaccuracy induced in nanoindentation measurements by the inherent pile-ups and sink-ins. Also, it was the intention to find out how the formation of pile-ups is dependant upon the crystal structure and orientation of the plane of indentation. Nanoindentation, Nanovision, scanning electron microscopy, electron dispersive spectroscopy and electron backscattered diffraction techniques were used to determine the sample composition and crystal orientation. Surface topographical features like indentation pile-ups and sink-ins were measured and the effect of crystal orientation on them was studied. The results show that pile-up formation is not a random phenomenon, but is quite characteristic of the material. It depends on the type of stress imposed by a specific indenter, the depth of penetration, the microstructure and orientation of the plane of indentation. Pile-ups are formed along specific directions on a plane and this formation as well as the pile-up height and the contact radii with the indenter …
Date:
May 2008
Creator:
Srivastava, Ashish Kumar
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
State accountability ratings as related to district size and diversity.
All Texas school districts were examined to determine the relationship of district size and diversity to the accountability ratings of selected Texas school districts and the implications of including all data in the accountability rating system. Eight large districts and 12 small districts were matched demographically utilizing data from the 2003-2004 school year. Information from the Texas Education Agency was accessed over 2003-2004 and 2004-2005. The ratings were found to be lowered from Recognized to Academically Acceptable with the inclusion of these groups 6 out of 20 times. These findings indicate that the Texas accountability system, in its current structure, excludes certain students based upon race and economic status and is not in compliance with what the law intended. This study should be replicated on a larger scale to assess its validity for a larger sample of small districts. Equity among states should be examined to provide information for a nationwide accountability system.
Date:
May 2008
Creator:
Starrett, Teresa M.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Alexander Scriabin (1871-1915): Piano Miniature as Chronicle of his Creative Evolution; Complexity of Interpretive Approach and its Implications.
Scriabin's piano miniatures are ideal for the study of evolution of his style, which underwent an extreme transformation. They present heavily concentrated idioms and structural procedures within concise form, therefore making it more accessible to grasp the quintessence of the composer's thought. A plethora of studies often reviews isolated genres or periods of Scriabin's legacy, making it impossible to reveal important general tendencies and inner relationships between his pieces. While expanding the boundaries of tonality, Scriabin completed the expansion and universalization of the piano miniature genre. Starting from his middle years the 'poem' characteristics can be found in nearly every piece. The key to this process lies in Scriabin's compilation of certain symbolical musical gestures. Separation between technical means and poetic intention of Scriabin's works as well as rejection of his metaphysical thought evolution result in serious interpretive implications. Music of Scriabin provides an excellent opportunity for a performer to find a proper balance between rational and intuitive. The lack of any of these qualities will impoverish his works, making their interpretation incomplete. Following one of main Scriabin's ideas - synthesis of all arts - this study approaches his music not from the narrow analytical, but broad synthetic standpoint. The …
Date:
May 2008
Creator:
Sukhina, Nataliya
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
ANTI Preference of the Pyramidalized Radical Center to the Two Fluorines in Difluoro Cyclic Compounds.
An extensive study of disubstituted cycloalkanes like CnH2n where n=3,4,5 and 6 using DFT((U)B3LYP/6-31G(d) and 6-311+G(2df,2p)) calculations is presented focusing on the effect of pyramidalization of the radical center. A potential energy surface (PES) analysis shows that the radical prefers to pyramidalize anti to the two cis fluorines in the disubstituted cycloalkanes. The degree of pyramidalization for 1,2-difluorocyclopropyl radical is 43.9o away from the cis fluorines whereas for 1,3-difluorocyclobutyl radical, 1,3-difluorocyclopentyl radical and 1,3-difluorocyclohexyl radical is 3.8o, 5.4o and 14.5o respectively away from the cis fluorines. The importance of this pyramidality effect in these compounds is discussed in context with the carbon-hydrogen bond dissociation energies (BDE's) because the preference of the radical centers to pyramidalize anti to the fluorines affects the bond dissociation energy. Importance of steric effect and unfavorable electronic interactions have been extensively explored in planar permethylated cyclobutadiene (Me4CBD) and cyclooctatetraene (Me8COT) using ((U)B3LYP/6-31G(d) and 6-311+G(2df,2p)) calculations. It is thought that steric interactions dominate electronic interactions in Me8COT, while this works opposite in case of Me4CBT. Instead, in Me4CBD the number of unfavorable electronic interactions between π bonds and out-of-plane hydrogens plays the dominant role in determining the relative energies. Interactions between the π bonds of CBD and …
Date:
May 2008
Creator:
Tanna, Jigisha
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library