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Chemistry homework Assignment

Chemistry homework Assignment

scale elements have been obtained earlier than and after every experi- ment from separate audio facet band spectra which have been derived from Hello and situated inside a number of hertz of the unique satellites. In every case, the earlier than and after scale elements agreed to lower than Zero.Zero01 Hz/cm.

For all seven temperature experiments described above, the typical scale issue by no means assorted by greater than Zero.02 Hz/cm, and most values have been inside Zero.01 Hz/cm of the typical, Zero.99 Hz/cm. Within the remaining temperature experiments, an audio facet band, generated by a frequency of Eight.6-9.2 Hz, was produced from one transition of the satellite tv for pc doublet, and measured with respect to the remaining transition about 1.5 Hz away. At any temperature, a most anticipated error of Zero.02 Hz/cm within the above common scale issue (Zero.99 Hz/cm) would introduce a most complete scaling error of Zero.03 Hz in Jcc however for many instances, the scaling error is regarded as lower than Zero.01 Hz. Nmr knowledge for Three are proven in Desk III.

Experimental Part 2.Three- Dideuterio-l,Three-butadiene (2). 2,Three-Dideuterio-2,Three-butanediol

was ready by discount of biacetyl with lithium aluminum deuteride in line with the process of Loewus, Westheimer, and Vennesland.32 The crude 2,Three-dideuterio-2,Three-butanediol was dis- tilled by means of a Vigreux column underneath vacuum, and the key frac- tion was collected at 89-92° (21 mm) (reported 95-105° (40 mm)).

2.Three- Dideuterio-2,Three-butanediol was acetylated within the regular man- ner33 utilizing an extra of acetic anhydride and pyridine. The crude product was distilled by means of a Vigreux column, and the key

(32) F. A. Loewus, F. H. Westheimer, and B. Vennesland, J. Amer. Chem. Soc., 75, 5018 (1953).

(33) L. F. Fieser and M. Fieser, “Reagents for Natural Synthesis,” Wiley, New York, N. Y., 1967, p 958.

6375

fraction of two,Three-dideuterio-2,Three-diacetoxybutane was collected at 94.Zero-94.5° (22 mm).

2,Three-Dideuterio-2,Three-diacetoxybutane (Three g) was added dropwise right into a heated Vycor column containing Vycor chips underneath an environment of N2 at 585°, utilizing the process of Shlechter, Othmer, and Model.34 The crude gaseous product was purified by passage by means of an ice-cooled entice, adopted by a bubbler containing 10% aqueous sodium hydroxide answer and a second bubbler con- taining water. The moist fuel was handed by means of a tube containing a weighed combination of carbon disulfide and hexamethyldisilane. The nmr tube, which was immersed in a Dry Ice-acetone bathtub, was evacuated and sealed underneath vacuum. The combination was discovered to be Eight.Three% (w/w) 2,Three-dideuterio-1,Three-butadiene (2) and Four.6% hexa- methyldisilane in carbon disulfide solvent.

1,1,Four,Four-Tetradeuterio-l,Three-butadiene (Three). 2,2,5,5-Tetradeuterio- 2,5-dihydrothiophene 1,1-dioxide was ready from sulfolene by alkaline deuterium trade in line with the tactic of Cope, Berchtold, and Ross.35 Eight exchanges yielded 99.Three% isotopic purity (by nmr integration). Recrystallization from 2:1 THF- pentane gave a mp 63-65° (reported mp 66.Eight-67.Three°).

The above dihydrothiophene 1,1-dioxide (5 g) was pyrolyzed at 130° to generate Three at a handy price. Gaseous Three was bubbled by means of two traps, every containing about 100 ml of 10% aqueous sodium hydroxide answer to take away the sulfur dioxide by-product shaped within the response. The purified Three was handed by means of a tube containing Drierite, and into two preconstricted tared nmr tubes containing recognized weights of hexamethyldisilane. The nmr tubes have been immersed in Dry Ice-acetone contained in a dewar flask. To be able to decrease boiling of three throughout excessive temperature experi- ments, one in all these stuffed nmr tubes was sealed underneath nitrogen at atmospheric strain. The second nmr tube, sealed underneath vacuum, was used for the remaining variable-temperature research. Each samples contained 11 % (w/w) hexamethyldisilane in neat Three.

Acknowledgment. The authors are grateful to the Nationwide Science Basis for Grant No. GP- 3815 which offered help for this work.

(34) N. Shlechter, D. F. Othmer, and R. Model, Ind. Eng. Chem., 37, 905 (1945).

(35) A. C. Cope, G. A. Berchtold, and D. L. Ross, J. Amer. Chem. Soc., 83, 3859 (1961).

Conformational Assessment of 2-Methylbutane1 Robert L. Lipnick and Edgar W. Garbisch, Jr.*2 Contribution from the Division of Chemistry, College of Minnesota. Minneapolis, Minnesota 55455. Acquired November 9, 1972

Summary: The AB2 deuterium-decoupled pmr spectrum of 2-methylbutane-d9 (1) was decided at ten tempera- tures within the vary —91 to +72°. The noticed temperature dependences of the three nmr parameters (va, vs, and Jab) have been ascribed to adjustments in conformer inhabitants with temperature (eq 1). These parameters have been subse- quently utilized in a least-squares Assessment to acquire quantitative estimates of AH and the intensive nmr parameters of conformers la and lb. The worth of AH for the equilibrium la ^ lb is 888 ± 18 cal/mol ( 5 = —1.376 eu). The torsional angle, a, for la was estimated to fall between 60 and 72° from the calculated vicinal coupling con- stant.

Rotational isomerism in 2-methylbutane has been

. noticed by Raman,Three infrared,Four ultrasonic,5 and thermodynamic6 strategies, and estimates have been fabricated from

(1) Offered partly by R. L. L. on the 23rd Congress of Pure and Utilized Chemistry, Boston, Mass., July 1971.

(2) Correspondence could also be directed to E. W. G., Heart for Utilized Analysis in Environmental Sciences, St. Michaels, Md. 21663.

(Three) G. J. Szasz and N. Sheppard, J. Chem. Phys., 17, 93 (1949). (Four) J. Ok. Brown and N. Sheppard, J. Chem. Phys., 19, 976 (1951). (5) J. M. Younger and A. A. Petrauskas, J. Chem. Phys., 25, 943

(1956). (6) D. W. Scott, J. P. McCullough, Ok. D. Williamson, and G. Wad-

dington, J. Amer. Chem. Soc., 73, 1707 (1951).

each the enthalpy distinction between the 2 potential conformers and their barrier to interconversion.

Szasz and Sheppard concluded from Raman3 that the enthalpy distinction for the equilibrium la lb was

Lipnick, Garbisch / Conformational Assessment of 2-Methylbutane

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L A

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6376

Determine 1. The 60-Mc/sec nmr spectra of 1 at (a) 35.5° with deu- terium decoupling, (b) 35.5° with out deuterium decoupling, and (c) the calculated theoretical spectrum utilizing the spectral parameters obtained from laocoon3 at 35.5°.

both lower than 200 cal/mol or larger than 1000 cal/mol. Brown and Sheppard4 drew no quantitative conclu- sions from their infrared research. Scott and coworkers6 concluded from their warmth capability measurements that the C, conformer, lb, is at the least a number of thousand cal/ mol much less secure than la, the C, conformer. Extra re- cently, Au-Chin,7 utilizing theoretical concerns, has estimated AH for la lb as 1.33 kcal/mol.

This work makes an attempt to verify by means of variable- temperature nmr that la is the extra secure conformer within the equilibrium la lb and to find out extra pre- cisely the enthalpy distinction between la and lb. As well as, the derived vicinal coupling constants will probably be used to estimate the torsional angle, a, for the Cj con- former.

Outcomes and Dialogue Beneath situations of deuterium decoupling, 2-methyl-

butane-t/g (1) offers rise to eight nmr transitions, corre- sponding to a spectrum of the sort AB2.Eight Preliminary values of va, vb, and Jab have been obtained from eq 1-Three,9 the place

have been subsequently inputed into iterative laocoon310 calculations together with the corresponding experimental frequencies of all eight transitions to acquire finest least- squares values of vK, vB, and JAb. Determine 1 exhibits un- decoupled and deuterium-decoupled spectra of 1 together with a laocoon3 computed spectrum.

These laocoon3 derived parameters have been used in- dependently to find out one of the best answer values to eq 411,1 s the place Paj and PbJ are the y’th of / intensive param- eters of conformers la and lb, and Ptf is the y’th of / noticed parameters on the /th of okay temperatures, <;. As answer of eq Four various all the unknowns, in-

P,j – , =

—AH AS Ptf – ¿V RTij + R (Four)

eluding AH and AS, was not achieved, it was discovered mandatory to cut back the variety of unknowns by one by means of assuming AS = —R In 2 (—1.376 eu), the statistical worth corresponding to 2 enantiomeric Cs conformers.14

Various necessities which have to be glad for the quantitative utility of eq Four to conformational Assessment have been mentioned critically.13 It’s important that P&j and Pb¡ each be temperature unbiased in order that the noticed temperature dependences, °, mirror solely adjustments in conformer inhabitants. We use as an operational criterion of this situation, the self-consis- tency of the unbiased eq Four answer values of AH offered by the respective nmr parameters and the chemical shift distinction, . These answer values of AH obtained within the single parameter calculations are offered in Desk I (options 1-Four). They’re seen to fall inside the possible errors of each other, and due to this fact meet our operational criterion for the temper- ature independence of the respective intensive param- eters. Due to this fact, it’s felt justified to make use of as probably the most dependable answer of eq Four these values obtained in a single mixed parameter calculation of vA, vB, and Jab (answer Four). This a number of parameter calculation results in an enthalpy distinction AH – 888 ± 18 cal/mol at AS = —1.376 eu for the equilibrium la ^ lb. Determine 2 exhibits the theoretical temperature dependences of va, vb, and Jab similar to answer 5 (Desk I) together with the experimental values of those parameters.

The derived vicinal coupling constants for conformers la and lb obtained in answer 5 of Desk I permit us to estimate the torsional angle, a, for the Ct conformer la, utilizing the theoretical relationship15 between dihedral angle, , and vicinal coupling, J

J = A(cos2 + n cos ) (5) In these calculations, the projected torsional angle, , in each la and lb is assumed to be 120°. For the reason that C,«

VA = Vl (1)

VB = (v¡ + Vl)¡2 (2) Jab = Vs[(vs — ve) + (v4 — n)] (Three)

va and vB are the chemical shifts of HA and HB (relative to hexamethyldisilane), and Jab is the vicinal proton coupling throughout the two,Three C-C bond. These preliminary values

(7) T. Au-Chin, Sci. Sínica, Three, 279 (1954). (Eight) See J. Lee and L. H. Sutcliffe, Trans. Faraday Soc., 55, 880

(1959). (9) E. W. Garbisch, Jr„ J. Chem. Educ., 45, 402 (1968).

(10) S. M. Castellano and A. A. Bothner-By in “Laptop Packages for Chemistry,” Vol I, D. F. Detar, Ed., W. A. Benjamin, New York, N.Y., 1968, pp 10-39.

(11) See ref 12 and references cited therein. (12) R. L. Lipnick and E. W. Garbisch, Jr., J. Amer. Chem. Soc.,

95, 6370 (1973). (13) E. W. Garbisch, Jr., B. L. Hawkins, and Ok. D. MacKay in “Con-

formational Assessment: Scope and Current Limitations,” E. Chiurdogu, Ed., Educational Press, New York, N. Y., 1971, pp 93-110.

(14) The entropy of blending is often used to account for any entropy variations between conformers. See E. L. Eliel, N. L. Allinger, S. J. Angyal, and G. A. Morrison, “Conformational Assessment,” Wiley. New York, N. Y., 1965, pp 11-12.

(15) M. Barfield and D. M. Grant, Advan. Magn. Resonance, 1, 149 (1965).

Journal of the American Chemical Society j 95:19 / September 19, 1973

Desk

I.

Resolution

Parameters”

of

Equation

1

Utilizing

Temperature

Dependences

of

Jab,

pa,

pb,

and

¿ab

at

Fastened

Values

of

5

6377

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odd Four Four Four

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33 Three odd Four Four Four

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o

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’two MMfnrt’t’t’£>-<fSnoowwCsir4CNiNfN<N<NrN(NN0NDNC—> — —<

-H-H+I-H-H-FI-H-H-H-H-H-H-H-H-H •nmr-O’P-‘—NOrfr-OOONDOOOCNONNommoooocintNp-infNrNocxO P-r-P-ON^C0000000OOOON0000

r-r-r-r-p-t-r-r-r-r-r-r-r-r-t— wnoownwwwoowfiwwfbw o*-»—o — — O’— — o—’–o — «—

efl •Eight

s

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-d e

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£ S’ c ‘o S .|

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= 25

s O

Determine 2. The experimental temperature dependences of pa (Zero), pb (·), and Jab (A), together with their theoretical dependences (strong strains). The theoretical dependences (strong strains) have been derived from the mixed parameter answer of eq 5 (answer 5 of Desk I).

conformer (lb) is symmetric, the derived coupling 16 is given by eq 6. For the C¿ conformer (la), the

Jb = Three.52 Hz = A(cos2 60° + n cos 60°) (6) corresponding coupling is given by eq 7,17 the place a is

= 7.06 Hz = -“-Four–· =

A(COS2 a + « COS a) + A(cos2 ( + a) + « COS ( + a)) 2

(7)

the torsional angle between the 2 gauche associated methyl teams. Software of eq 5 to the experi- psychological vicinal couplings for the collection ethane, propane, and isobutane permits an estimate to be fabricated from the worth for A for a collection of hydrocarbons obtained by rising methyl substitution of an ethane skeleton. For ethane, propane, and isobutane, the experimental vicinal coupling, JviCinai, is given by eq Eight, the place 0g =

_

2/e + _

«’vicinal ^

2^(cos2 + n cos 0g) + /Four(cos2 Four + n cos Four) 1 (Eight)

60° and = 180°. Simplification of eq Eight results in eq (16) Ja and Jb refer right here to the vicinal interproton couplings throughout

the two,Three C-C bond for conformers la and lb, respectively. (17) Je and Jt discuss with the gauche and trans vicinal interproton cou-

plings throughout the two,Three C-C bond for conformer la.

Lipnick, Garbisch / Conformational Assessment of 2-Methylbutane

6378

N

Determine Three. The dependence of A (eq 10) as a perform of the variety of methyl teams substituted on ethane for ethane (a), propane (b), isobutane (c), cyclohexane (d), and butane (e). The triangles (f) point out values of A for 2-methylbutane similar to a = 60, 66, and 72°.

9. In Determine Three, A is plotted as a perform of the quantity A 3Jvicinal/1 *50 ^Aioinal (9)

of methyl substitutions, N, for the collection ethane,18 propane,19 isobutane,20 butane,21 and cyclohexane.22 The qualitative lower in A with rising substitu- tion in all probability limits A to a worth no larger than 13.6 Hz, the most important such coefficient obtained for a disub- stituted ethane. This worth of A is discovered to corre- spond to = Zero.02 and = 72° upon simultaneous solu- tion of eq 6 and seven. The decrease limiting worth for is 60° ( = Zero.10, A = 11.7 Hz), similar to no in- crease within the regular sp3-sp3 torsional angle. The gauche conformer of «-butane (A = 12.56, = Zero.11), an analogous system with one gauche methyl-methyl inter- motion, has been discovered to be skewed 66°.21·23 The gauche butane worth for the torsional angle, which might be one of the best empirical estimate for a, falls be- tween the decrease and higher limits (60-72°) obtained above.

It’s of curiosity to match the enthalpy change la lb (AH = +888 ± 18 cal/mol) with that discovered for the comparable butane equilibrium 2a +; 2b (AH =

ch3 h 2a 2b

+681 ± 35 cal/mol).21 In each equilibria, conformer a is the energetically extra favorable kind as a consequence of a further methyl-methyl interplay current in b. For gauche butane (2b), this steric interplay is par- tially relieved by a rise within the torsional angle. The Cs conformer of 2-methylbutane, lb, incorporates two symmetrical methyl-methyl interactions, and can’t bear torsional deformation. If the extra enthalpy change for la lb over 2a ;=± 2b of 207 cal/ mol is because of unrelieved methyl-methyl interactions,

(18) R. M. Lynden-Bell and N. Sheppard, Proc. Roy. Soc., Ser. A, 269, 385 (1962).

(19) D. R. Whitman, L. Onsager, M. Saunders, and . E. Dubb, J. Chem. Phys., 32, 67 (1960).

(20) J. S. Waugh and F. W. Dobbs, J. Chem. Phys., 31, 1235 (1959). (21) P. B. Woller and E. W. Garbisch, Jr., J. Amer. Chem. Soc., 94,

5310 (1972). (22) E. W. Garbisch, Jr., and M. G. Griffith, J. Amer. Chem. Soc.,

90, (6543 1968). (23) Ok. Kuchitsu, Bull. Chem. Soc. Jap., 32, 748 (1959).

then every such interplay is equal to a rise in enthalpy of roughly 104 cal/mol. This anal- ysis would predict an enthalpy distinction of approxi- mately 785 cal/mol (681 + 104) for the equilibrium 3a =5 3b of two,Three-dimethylbutane. This estimate is in

qualitative settlement with the worth of Zero.95 kcal/mol,24 obtained by ultrasonic absorption, through which the ex- pected tolerance is roughly ± 400 cal/mol.25

Nmr Spectral Determinations. Excessive decision deu- terium-decoupled nmr spectra have been taken on a modified Varían A-60 nmr spectrometer, as described pre- viously.12 Spectra have been obtained from a neat pattern of 2-methylbutane-<f9 containing ~10% (v/v) hexa- methyldisilane, and sealed underneath vacuum. Spectra have been decided at ten temperatures from —91 to +72°, and 12-22 spectra have been recorded at every temper- ature. Frequencies for every transition have been calculated from the middle at half-height of every peak from audio facet band calibration. Scale issue corrections ranged from Zero.984 to Zero.991 Hz/cm. Common values and the corresponding customary deviations have been calculated for every transition and any frequency values whose devia- tions have been larger than twice the usual deviation for that transition have been routinely discarded. This course of was repeated routinely till experimental values have been now not discarded.

Preliminary values for ¡ , vb, and As which have been obtained from eq 1-Three have been used as enter for least-squares lao- coon3 calculations. For every temperature, any transi- tion whose common experimental frequency differed from the corresponding calculated worth by greater than twice the laocoon3 calculated customary deviation was discarded, and allowed to fluctuate in a second iterative calculation. Desk II exhibits the ultimate outcomes for ten temperatures.

Desk II. Temperature Dependences of the Pmr Parameters for 1

Temp“ VAb -7abc 6abc

71 .7 82.321 (Zero.004)“ 68.796 (Zero.004)“ 6.623 (Zero.004)“ 13. 525 51. Three 82.056 (Zero.007) 68.605 (Zero.007) 6.662 (Zero.007) 13 .451 30. Eight 81.717 (Zero.Zero10) 68.381 (Zero.009) 6.716 (Zero.009) 13 336 19 7 81.563 (Zero.007) 68.258 (Zero.006) 6.739 (Zero.006) 13 .305

-Four. Three 81.180 (Zero.015) 67.994 (Zero.013) 6.760 (Zero.013) 13 .186 -20. 5 80.933 (Zero.004) 67.792 (Zero.004) 6.779 (Zero.004) 13. 141 -41 .6 80.593 (Zero.Zero19) 67.575 (Zero.Zero19) 6.792 (Zero.017) 13 .Zero18 -61 .7 80.227 (Zero.005) 67.283 (Zero.005) 6.855 (Zero.005) 12 .944 -80 .6 79.866 (Zero.Zero10) 67.029 (Zero.Zero10) 6.912 (Zero.009) 12. 837 -91 2 79.703 (Zero.015) 66.900 (Zero.015) 6.923 (Zero.013) 12. 803

“In °C; correct to ±1°. 6 Downfield from HMDS in Hz. c In Hz. d Values in parentheses are customary deviations.

Experimental Part 2-Methylbutane-+ was ready in three steps in line with

Scheme I.

(24) J. H. Chen and A. A. Petrauskas, J. Chem. Phys., 30, 304 (1959).

(25) E. Wyn-Jones and R. A. Pethrick, Prime. Stereochem., 5, 240 (1970).

Journal of the American Chemical Society j 95:19 / September 19, 1973

6379

Scheme I

CD3MgI-Et20

Cl Cl

OH CD:i

A CD3 CD,

Four 5

jTsCl/Py

CD, OTs CD,

aX LiAlH4-THF /

CD;, CD, CD; CD.

2-Methyl-Three-butanoW9 (5). 2-Methyl-Three-butanol-rfs (5) was pre- pared utilizing a process just like that reported by Huston, Jack- son, and Spero26 for the undeuterated compound. The equipment, which consisted of a 500-ml three-necked flask fitted with a Hof- mann condenser, dropping funnel, nitrogen consumption, and drying tubes, was dried in an oven for a number of hours, and flushed with dry nitrogen after meeting. Reagent grade magnesium turnings, 5.20 g (Zero.214 mol), and a small amount of methyl-rf3 iodide (Stohler, 99.5% D) have been added. The combination was stirred vigorously and the remaining methyl-^ iodide (30 g complete or Zero.211 mol), dissolved in 100 ml of anhydrous ether, was added dropwise over a 1.5-hr interval. Following the addition, the combination was stirred for a further Zero.5 hr. Chloroacetyl chloride, 5.96 g (Zero.0527 mol), was dissolved in 100 ml of anhydrous ether, and added dropwise to the Grignard over a 1-hr interval in order to take care of a gentle reflux. The ether was eliminated by distillation and the residue heated for two days at 95-100°.

The tarry residue was hydrolyzed by addition of ice, 100 ml of ether, and concentrated hydrochloric acid till the combination was simply acidic. The aqueous section was extracted ten instances with about 300 ml of ether, and the ether was dried over anhydrous potassium carbonate and sodium sulfate, and filtered. The filtrate was dis- tilled slowly by means of a vacuum-jacketed Vigreux column. A number of fractions have been collected and analyzed by glc. The ultimate two frac- tions (2.80 g, 55% principle), bp 94-112° (lit. bp 112° (734 mm)), have been appropriate for the subsequent response. The undecoupled nmr spectrum of

(26) R. C. Huston, R. I. Jackson, and G. B. Spero, J. Amer. Chem. Soc., 63, 1459 (1941).

5 reveals three broad alerts at 1.6 (C-H ß to OH), 2.1 (C-H a to OH), and three.5 (OH), with the anticipated integration ratio 1:1:1.

Methyl-Three-butanol-c/g Tosylate (6). To a stirred answer of two.35 g (Zero.0242 mol) of 5 in 20 ml of dry reagent grade pyridine which was cooled in an ice bathtub was added dropwise an answer of 9.25 g (Zero.0484 mol) of p-toluenesulfonyl chloride in 20 ml of pyridine. Pyridinium chloride crystallized out after about 15 min. The reac- tion combination was sealed in a flask and left for two days at 7°. After this time, the combination was poured over ice and concentrated hydro- chloric acid added till the resultant combination was distinctly acid. The product was extracted 3 times with ether, and the mixed ether extracts have been washed with 5% hydrochloric acid and water after which dried over a combination of anhydrous potassium carbonate and sodium sulfate. After filtration, the ether was eliminated on a rotary evaporator, and the residue was dissolved in pentane. The pentane was distilled and the method was repeated till no water droplets have been noticed within the distillate. The dry tosylate (6) was recrystallized 3 times from pentane, yield 5.36 g (88.5%), mp 20—21 °. The undecoupled nmr spectrum of 6 reveals an AB quartet centered at 7.6 (fragrant), a broad doublet at Four.5 (H a to -OTs), a singlet at 2.Four (fragrant methyl), and a múltiple! at 1.Eight ( ß to -OTs), with the anticipated integration ratio Four:1; Three:1.

2-Methylbutane-ífg (1). Reagent grade tetrahydrofuran (30 ml) was distilled from lithium aluminum hydride right into a dry three- necked 100-ml flask. The flask was fitted with a condenser and a pressure-equalizing dropping funnel with an consumption for dry nitro- gen. Lithium aluminum hydride, 2.Zero g (Zero.Zero52 mol), was added slowly by means of a powder funnel. The stirred combination was heated in an oil bathtub at 65-70°, and three.Zero g (Zero.Zero12 mol) of 3 times re- crystallized 5 dissolved in 20 ml of dried tetrahydrofuran was added dropwise. The vaporized hydrocarbon, 1, was performed by means of a micro purification prepare linked to the producing equipment, consisting of bromine water (to take away 2-methyl-2-butene which was beforehand detected by glpc), sodium thiosulfate answer, and two ethylene glycol bubblers (to take away tetrahydrofuran solvent), and a tube of Drierite. Purified 1 was performed lastly by means of a finely drawn polyethylene tube right into a constricted nmr tube im- mersed in a Dry Ice-2-propanol bathtub. A earlier undeuterated pattern, ready and purified in the identical means, was discovered by glpc to be pure.

Acknowledgment. The authors are grateful to the Nationwide Science Basis for Grant No. GP-3815 which offered help for this work.

Stereochemical Management of Reductions. III. An Method to Group Haptophilicities1

Hugh W. Thompson* and Richard E. Naipawer2

Contribution from the Division of Chemistry, Rutgers College, Newark, New Jersey 07102. Acquired January 15, 1973

Summary: The tetrahydrofluorene system 1, angularly substituted with a collection of practical teams R, has been catalytically hydrogenated over a palladium catalyst. For every practical group the share of cis isomer within the product is taken as a measure of that group’s tendency, termed haptophilicity, to be sure to the catalyst sur- face throughout olefin discount and thereby to implement addition of hydrogen from its personal facet of the molecule. The character of haptophilic exercise and its correlation with varied measures of group digital traits and dimension are mentioned.

For the reason that work of Linstead on the discount of phen-

anthrenes,Three most of the stereochemical points of heterogeneous catalytic hydrogenation have been

(1) (a) Abstracted partly from the Ph.D. Thesis of R. E. N. (b) Half II: H. W. Thompson and R. E. Naipawer, J. Org. Chem., 37, 1307 (1972).

(2) NASA Predoctoral Trainee, 1966-1967. (Three) R. P. Linstead, W. E. Doering, S. B. Davis, P. Levene, and R. R.

Whetstone, J, Amer. Chem. Soc., 64, 1985 (1942), and following articles.

made understandable when it comes to the strategy, match, and binding of the reducible molecule to the floor of the catalyst.Four These ideas have been utilized with specific success to molecules whose geometry or substituents current extreme steric hindrance to this

(Four) (a) R. L. Burwell, Jr„ Chem. Rev., 57, 895 (1957); (b) S. Siegel, Advan. Catal. Relat. Subj., 16, 123 (1966).

Thompson, Naipawer / An Method to Group Haptophilicities

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