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A Study of the Charge Distribution in Unconjugated Thiocarbonyl Compounds: a Comparison with Carbonyl and Imine Chromophores

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A Study of the Charge Distribution in Unconjugated Thiocarbonyl Compounds: a Comparison with Carbonyl and Imine Chromophores South Dakota State University Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange Electronic Theses and Dissertations 1974 A Study of the Charge Distribution in Unconjugated Thiocarbonyl Compounds: a Comparison with Carbonyl and Imine Chromophores John Yuchu Lee Follow this and additional works at: https://openprairie.sdstate.edu/etd Recommended Citation Lee, John Yuchu, "A Study of the Charge Distribution in Unconjugated Thiocarbonyl Compounds: a Comparison with Carbonyl and Imine Chromophores" (1974). Electronic Theses and Dissertations. 4734. https://openprairie.sdstate.edu/etd/4734 This Thesis - Open Access is brought to you for free and open access by Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. For more information, please contact [email protected]. STUDY CB1'RGE DISTRIBUTION UNCONJUGATED A OF THE Id THIOCARI30NYL COMPOUNDS: COMPARISON A WITH THE CARBONYL AND IMINE CHRO!-DPHORES . BY JOHN LEE YUCHU �.UTH _DAKOTA STATE UNIVERSITY LIBRARY thesis A su:C:-:iitted fulfill::1ent of the the in partial requirer,ents for degree in Master of Cheriistry, Science, ��jor South Dakota State Unive1·sity 1974 '1, I A STUDY OF THE CHARGE DISTRIBUTION IN UNCONJUGATED THIOCARBONYL COMPOUNDS: A COMPARISON WITH THE CARBONYL AND IMINE CHROr-OPHORES Abstract JOHN YUCHU LEE Under the supervision of Dr . James Worman Via a literature search it has been shown, by means of the ira spectra of thioamides, the dipole moments of thiocarbonyl compounds , the basicity of thioamides and thioureas, the acidity of carboxylic acids carrying a substituent with the thiocarbonyl function, LCAO-b method, and proton· chemical shifts, that the thiocarbonyl group me has tendency to give a greater mesomeric interaction than the (�) carbonyla group (£) with electron donating heteroatoms. II r;; -q�c - x -dc - x Io e I = <B I = - tc x c x@ (.£) (_�) A comparison of the charge distribution in unconjugated thio- carbonyl carbonyl (d) , and imine chromophores is made by (£), (_g) means of surveying the dipole moments of several small molecules, calculating the forces constants from the ir absorption frequencies, measuring the bond distances by x-ray, and observing the proton chemical shifts in the nmrd spectra. The use of the electronic ab- sorption spectra, molecular orbital theory, and mass spectrometry are also included. All data support the hypothesis that the thiocarbonyl chromophore has more ionic contribution to the resonance hybrid than is present in or This is not predictable on the basis of the electronega- (£) (�). tivity of the heteroatoms . - 0- N/ s 0 0 0 II II II 0 c o + c o + + c /\ /\ I\ (£) (£) (�) a ir = Infrared . CAO = Linear Combination of Atomic Orbitals chr. M) = Molecular Orbital d nmr = nuclear magnetic resonance A STUDY OF THE CHARGE DISTRIBUTION IN UNCONJUGATED THIOCARBONYL COMPOUNDS: A COMPARISON WITH THE CARBONYL AND IMINE CHARO�DPHORES Th is thesis is approved as a creditable and.independent investigation by candida te for the degree, Ma ster of Science, and is acceptable as meeta ing the thesis requirements for this degree. Acceptance of this t.hesis does not imply that the conclusions reached by the candidate are neces sarily the conclusions of the major depart­ ment. sis Adviser Da e M' / f Head, Chemistry Department Da te Emma Lee and G. To Ornodt ACKNOWLEDGMENTS wish to express my deepest tha nks to Dr. James J. Worman, under I whose direction this thesis was prepared, for his continuous encour­ agement and helpful suggestions during the course of this investi­ gation. also would like to thank all the staff in the Chemistry I Depa rtment. At last, my thanks goes to Mrs. Betty Prunty for typing this thesis. JYL TABLE OF CONTENTS Page HISTORICAL SURVEY OF CHARGE DISTRIBUTION IN CON­ JUGATED CARBONYL TH IOCARBONYL COMPOUNDS • 1 AND PURPOSE . 11 RESULTS . 12 METHODS AND Dipole Moment 12 Infrared Spectroscopy • • 13 X-Ra ·� . • • • • • • • • • . 16 Nucleary Magnetic Resonance Spectroscopy 18 Electronic Spectroscopy • • • • • • • • 24 Mass Spectra 24 . • • • • • Melting Point ••• 26 ••••••••• DISCUSSION . 27 38 CONCLlJS:!:ONS . EXPERIMENTAL . 39 . of Instrumentation Used 39 Description • • . • Preparation of Diethylketals • 39 . • • • ne 40 2,2-Diethoxy-1�3-diphenylpropa . • • • • • • • • 40 Preparation of Thiones . • . • • • • • • • 40 l,3-Diphenyl-2-propanthione XXXII . • 41 ( ) Preparation of Tetramethyl-1,3-cyclobutanedithione XXIX •• 41 Preparation of N,N'-Dicycloheptyl-2,2,4,4- ( ) tetramethyl-l,3-cvclobutanediimine • • • • • • • • • 42 Preparation of the N-n-butyl imine of 1, 3- diphenvl-2-propanone XXXIII . • • • • • 43 ( ) REFERENCES 44 APPE IX 47 ND LIST OF TABLES Table Page 1. DIPOLE JvOMENT DEBYE OF SOME CARBONYL AND THIOCARBONYL COMPOUNDS( ) R1 C = X X = 0, S . 1 R2 ) ( ) . 2. CALCULATED VALUES FOR THE SYSTEMS VII-XVII , AND�µ VALUES FOR µ,TIVII-� AND XII-XVII IN DEBYE( UNITS.) THE DIRECTION IS( C ) X ( ) • . 3 • • • • • . • • 3. ACID DISSOCIATION__... CONSTANTS . 7 4. PROTON CHEMICAL SHIFTS OF THE METHYL GROUPS OF ACET. AMIDE AND THIOACETAMIDE • • • 9 • • • • • • • • • • • • 5. DIPOLE M)MENTS OF SOME SIMPLE MOLECULES 12 6. INFRARED SPECTRA OF 2,2,4,4-TETRAMETHYL-l,3- CYCLOBUTANE-DIONE, 2,2,4,4-TETRAMETHYL-l,3- CYCLOBUTANE-DITHIONE, THE IMINE OF 2;2,4,4- TETRAMETHYL-l,3-CYCLOBUTANEDIONE, 1,3-DIPHENYL- 2-PROPANONE,l,3-DIPHENYL-2-PROPANETHIONE, AND THE IMINE OF l,3-DIPHENYL-2-PROPANONE •• 13 • • 7. FORCE CONSTANTS CALCULATED FROM TABLE 6 14 8. DOUBLE-BOND DISTANCES FROM THE CRYSTAL SffiUCTURES OF 2,2,4,4-TETRAMETHYL-l,3-CYCLOBUTANEDIONE,26 2,2,4,4-TETRAMETHYL-l-3-CYCLOBUTANEDITHIONE,27 AND 8 THE IMINE OF 2,2,4,4-TETRAMETHYL-l,3-CYCLOBUTANEDIONE2 16 9. NMR SPECTRA OF 2,2,4,4-TETRAMETHYL-l,3-CYCLOBUTANEDIONE, 2,2,4,4-TETRAMETHYL-l,3-CYCLOBUTANEDITHIONE, THE IMINE OF 2,2,4,4_TETRAMETHYL-l,3-CYCLOBUTANEDIONE, 1,3- DIPHENYL-2-PROPANONE, 1,3-DIPHENYL-2-PROPANETHIONE, NYL-2-PROPANONE OF 1,3-DIPHE • AND THE IMINE • • 18 • • 10. PROTON CHEMICAL SHIFT OF METHYLENE HALIDES X F, C 1, Br, I 1 -CH -X, • • 9 = • • • • ( 2 ) 11. ELECTRONEGATIVITY OF HALOGEN ELEMENTS 20 · Table Page 12. PROTON CHEMICAL SHIFT OF METHYL HAL IDES • 21 13. ELECTRONIC SPECTRA OF l, 3-DIPHENYL-3�PRO­ PANETHIONE33 AND 2, 2, 4,4-TETRAMETHYL-l,3- CYCLOBUTANEDITHIONE . • • . 24 • • • • • • • • • . 14 . MASS SPECTRA44 OF 2, 2, 4, 4-TETRAMETHYL-l,3- CYCLOBUTANEDIONE, 2, 2, 4, 4-TETRAMETHYL-l, 3- CYCLOBUTANEDITHIONE, THE IMINE OF 2,2, 4, 4- TETRAMETHYL-l,3 -CYCLOBUTANEDIONE • • • • • 25 15. MASS SPECTRA45 OF 1,3-DIPHENYL-2-PROPANONE, 1, 3-DIPHENYL-2-PROPANETHIONE, AND THE IMINE OF. 1, 3-DIPHENYL-2-PROPANONE . •••• •••• . 25 . 16. MELTING POINT OF 2,2, 4,4-TETRAMETHYL-l, 3- CYCLOBUTANEDIONE, 2, 2, 4, 4-TETRAMETHYL-l,3- CYCLOBUTANEDITHIONE, THE IMINE OF 2,2, 4,4- TETRAMETHYL-l,3 -CYCLOBUTANEDIONE 26 ••••• LIST OF FIGURES Figure Page 1. Double-bond distances vs. different functional groups • • • • • • • • • • • • • • • • • . 17 2. Proton chemical shifts of methylene vs. the electronegativity of halogen elements . 20 . 3. Proton chemical shifts of methyl halides vs. the electronegativity of halogen elements ••••. 21 4. Comparison of chemical shifts of methyl hydrogens of 2,2,4, 4-tetramethyl..:l ,3-cyclobutanedione, 2,2,4,4- tetramethyl-l, 3-cyclobutanedithione and trans-N,N'­ dicycloheptyl-2,2,4, 4-tetramethyl-l, 3-cyclobutane- di imine • • • • • • • • • • • • • • • • • • • • • • 22 5. Comparison of chemical shifts of methylene hydrogens of 1,3-diphenyl-2-propanone, l,3-diphenyl-2-pro­ panethione, and N-n-butyl-1, 3-diphenyl-2- propaneimine . 23 . 6 . Energy diagram for nmr . 28 . 7. Diamagnetic shielding of nucleus by circulating . electrons . 29 . Perturbation of electron cloud around a proton by s. inductive withdrawal by an electronegative substituent (X) . 30 • • • • • • • • • • • • • . • • • 9. Representative atomic orbitals 32 ••••••••• 10. Valence electron orbitals of the sulfur atom 33 •• 33 ll. A 2p-2p TT�bond • • • • 12. A sp-3p rr-bond . 34 • • • • • • 34 13. A sp-3d bond •• . 14 . ·A sp2-3p cr-bond, partial 2-3p rr-bond, and partial 2p-3d rr-bond • • • • • • • • • • • • • • • • • • • • • • • 35 15 . ·Ionic mechanism of dimeriza ti on of two thiocarbonyl groups 36 • • • • • • • • • • • • • • HISTORICAL SURVEY OF CHARGE DISTRIBUTION IN CONJUGATED CARBONYL AND THIOCARBONYL COMPOUNDS 2 Luttringhaus et fil· observed1' that the dipole moments (Table 1) of thiocarbonyl compounds exceed those of the corresponding carbonyl compounds if, and only if, subs tituents c9pable of strong mesomeric electron release were present in the molecule (1,-VI). < I foot r.. @ C = s = c - y ( ) s9 - c = y > Se - y ffi I (11.)I (III)I (1.) < I " oe - = c C.·- y ( ) 08-c=yffi c..; y - O= > m (IV) (VI) (y) TABLE 1. DIPOLE MO��NT (DEBYE) OF SOME CARBONYL THIOCARBONYL AND COMPOUNDS R 1 = = 0, S) x R (X 2/"'c R µc = o µc = s (µc=o-µc=s) 1 R2 .6µ, 2 Cl Cl 1.18 0. 8 +0.903 CH o CH30 . 3 0.87 0.90 0 0 33 - CH S CH3S 1. 3 0.74 -0.59 6 CH3 3.74 4.7 1 02 (CH3)2N . 3 4.44 - p-CH oc H p-CH30C6H4 3 6 4 . 90 -0.54 3.54 3.94 -0.40 p-CH3SC6H4 p-CH3SC6H4 2 Janssen3 reproduced this mesomeric tendency by a simple LCAO-MO method. A model based on two considerations, in order to select 7 parameters , 4,5,6 was chosen: ,8 1. The c-s and c=s bonds are polar. 2. Sulfur does not form double bonds as do first-row elements. With this model calculations were performed according to Huckel's LCAO procedure , modified by the w-technique , 9,10 until self-consistency was . obtained. The result showed that both an element of electron at­ traction and a low resonance integral are required for the thiocarbonyl group in the present approximation in order to bring out the general polarization characteristics observed.
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