The Reaction of Vitamin K,
Fred H. Greenberg, Kwok Kee Leung, and Martin Leung
with Sodium Bisulfite
SUNY-College at Buffalo Buffalo, New York 14222
An undergraduate organic experiment
There are few experiments that illustrate kinetic and thermodynamic control of a reaction. We wish to describe one such experiment in which the reaction under study is an example of nucleophilic addition to unsaturated carbon. Other features that may be emphasized are base-induced Belimination, keto-en01 tautomerism, and the power of nmr spectroscopy in structure determination.
quiuoue does not appear in the nmr spectra of the products. Therefore, the products do not have alkene double bonds between carbons 2 and 3 and cannot arise from addition to the carbonyl group. Treatment of vitamin K3 with sodium bisulfite leads to two addition compounds, I and IV, with the major product determined by conditions of reaction time and temperature.
0 Vitamin KI
m
Vitamin K,
A synthetic substitute for vitamin KI, which is necessary for blood clotting, is the structurally related compound 2-methyl-1,4-naphthoquinone,designated menadione or vitamin K8.' The latter quinone can be administered in drinkable form as a water soluble bisulfite addition compound whose medicinal effectiveness presumably results from regeneration of the vitamin in basic intestinal fluid via elimination of sodium bisulfite. The formation of an addition compound from reaction of sodium bisulfite and vitamin K3 is an example of nucleophilic 1,4-addition to an a,&unsaturated ketone. That the reaction does not occur by 1,2-addition to the carbonyl group is inferred from comparison of the reactant's and products' nmr spectra, shown in Figures 1 4 . The long range coupling between the methyl group and the vinylic proton in the nmr spectrum of the
' S T E ~ ~ EP.RG, . (Editm), "The Merck
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Index," Merck and
Ca. Inc., Rahwsy, N. J., 1968, p. 652. The structures of these compounds have been the subject of M., MOORE,M. B., several investigations. (a) CARMACK, AND BALIS,M. E., J . Amer. Chem. Soc., 72, 844 (1950); (b) BOCHVAR, D. A., AND SHEMYAKIN, M. M., J. Ga.Chm. (USSR), 16, 2033 (19461, C.A., 42, 895 (1946); (c) MENOTTI, A. R., J. Amw. Chem. Soc., 65,1209 (1943); (d) BAKER, B. R.,DAVIES, T. H., MCELROY, L., AND CARLSON, G. H., J . Amer. Chm. Soc., 64, 1096 (1942). The structures deduced from the nmr spectra are in agreement with the assignments in references s, c, and d but in disagreement with reference b.
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Mild warming of the reactants for a short time predominantly affords I which arises from attack of bisulfite ion a t carbon 2. Heating at reflux for an extended period yields IV from addition of bisulfite ion to carbon 3. To verify that different products are obtained under different conditions, both compounds are treated with dilute aqueous sodium hydroxide. Only I will eliminate sodium bisulfite, according to the following scheme, to yield a precipitate of the quinone.
+ Ha +
+
542The problem of the experiment is to carry out the reaction under both conditions, determine which product has which structure2 and understand the factors governing the course of the reaction. The structures follow immediately from their nmr spectra. Vitamin Ka
~ a +
Experimental Procedure
If one student is doing both reactions start the high temperature reaction first and while it is refluxing carry out the low temperature reaction. I t is essential to use CLEAN glassware. Even traces of dust will prevent precipitation of the product.
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Figure 1 . Nmr spectrum of CDCb; H. 2.1 8, H, 6.78, H, expanded five-fold.
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2.methyi-1.4-naphthoquinone, Solvent: 8.0. H. and H, m e &own
7.66, Hd
Figure 3. Nmr spectrum of the high temperature product. Solvent: DMSO-ds; Water: 3.47, DMSO-ds: 2.48 lmultiplet), H, 2.54, Ha 12.00,
H, 7.3-8.2.
Figure 2 . Nmr spectrum of the low temperature product. D 2 0 ; Water4.75, H. 1.67, Hs= Hv 3.37, H, 7.7-8.0,
Figws 4. Nmr spectrum of the high temperature product. . 2.72, H.7.3-8.1. D 2 0 ; W a k e 4.93. H
Low Temperature Reaction. Place in a 25-ml Erlenmyer flask approximately 0.5 g of Zmethyl-l,4naphthoquinonea and about 7 ml of a. saturated solution of sodium hisulfite. Warm gently on the steam cone-not longer than 5 min-with occasional shaking to effect solution of most of the quinone. If all of the quinone does not dissolve filter the mixture through a small cotton-plugged funnel into a CLEAN 25-ml Erlenmyer. A minimum of cotton should be used to avoid loss of solution through absorption. On cooling in an ice hath the filtrate provides the solid bisulfite addition compound. A seed crystal (obtained from the instructor)' may he added to promote orystallization. Filter with vacuum using a. Hirsch funnel, wash with a few drops of cold ethanol and dry on the aspirator. Recrystallieation is omitted. Melting points: the compound loses water of hydration at 100-llODC and may melt anywhere from 115140°C with decom~ositian. The revorteds value is 154-157' (dec.). Higher Temperature Readion. In a 2.5-ml ST 19/22 flask place approximately 0.5 g of Zmethyl-1,4-naphthoquinone, 8 ml of a saturated solution of sodium hisulfite, and a. boiling chip. Heat at reflux for 60 min or more using a microburner. Some bumping may occur. After hesting allow the mixture to cool and chill in an ice hath. Remove any unreacted quinone by filtering through cotton. Add 5 ml of a. saturated potassium chloride solution to the filtrate and cool in an ice hath. (The potassium salt precipitates more readily than the sodium salt.) If the product does not appear immediately add a seed crystall' and store the corked, labeled flask in a. refrigerator. Collect the precipitate by vacuum filtration, wash with a few drops of cold ethanol and dry on the filter. Since the wet product deteriorates in air it should he quickly dried and stored in a vial. Melting point: 177-180°C with decomposition. The literature5 value is 193-196°C (dec). Idalificatwn. The fact that different products are obtained under different conditions can be tested by treating both products with aqueous sodium hydroxide. One of the products eliminates the elements of sodium hisulfite and regenerates 2 methyl-1,4-naphthoquinone thereby providing a clue to the
identity of the addition products-only one of the structures (I, 11, 111, I V ) would NOT react in this fashion. Dissolve a s m d sample (-15 mg) of each product in 1-2 ml of water in two different test tubes and add 0.1 M sodium hydroxide solution dropwise to each tube. The immediate effect is to he noted in each ease. Hand in the products in laheled vials and obtain reproductions of their nmr speetrs.
Solvent:
Interpreting the Experiment
The following "program" serves as an aid to students in interpreting the experiment. 1 ) Decide which energy profile below corresponds to the formation of the high and low temperature products and draw the structures of the appropriate intermediates and oroduots.
a Eastman Kodsk #5185, 100 g., $7.75. The lab preparation of 2-methyl-1,4-naphthoquinone from oxidstion of ZmethylL. F., "Organic naphthalene has been described. FIESER, Exveriments." 2nd Ed.., Ravthenn Education Co.. Lexineton. " , M&., 1968,'~.246. 'Mendione sodium bisulfite is available from M m n RP search Laboratories, 136 Liberty St., New York, N. Y. 10006, Catalog #15000-837, 25 g., $3.50. "ee reference (c) in footnote 2 above. We will he happy to furnish samples on request.
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2) Is 11or 1 9 the more stable (lower energy) intermediate cmbanion? a. Which carbanion is secondary? b. Which carbanion is tertiary? e. The order of stabiility of carboninm ions is primary < secondary < tertiary. d. The order of stabiility of earbanions is primary secondary tertiary. e. Why is 1- more stable than I-? 3) Which activation energy leading from the starting materials to 11and 11is the smaller? 4) Is I, or 11formed faster? 5) The formation of Pz involves 4 steps (reactions) as shown by the diagram in question 1. How many steps lead to PI? 6) %oh of the steps leading to PI and PI is the slowest? 7) Which step is rate controlling? 8) Which product is formed faster? 9) Which product is the more stable? 10) When two competing reactions differ in activation energy the reaction with the lower activation energy proceeds faster. The product obtained from the faster reection is said to he kinetically controlled. Which product is obtained as a. result of kinetic control? 11) When two competing reactions differ in activation energy and sufficient heat is applied to surmount the energy barrier for both reactions the most stable product will predominate provided that the two products are interconvertible or that the faster reaction is reversible. Under these conditions thermodynamic control leads to the more stable product even though it is formed in the slower reaction. Which product is obtained as s, result of thermodynamic control?
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12) Suggest a reason why P- is more stable than P-. 13) Which reaction has the largest activation energy? (a) NaHSOa Vit Ka-11 (b) I,+Pl (c) NaHSO, Vit I4 11 (d) 1 2 + P2 (e) 11+ Pn or the reverse reaction of a, b, c, d, or e. 14) Which reaction mieht be described as irreversible? 15j (a) What productkould be obtained if sn aqueous sohtion of PI were heated a t reflux? (h) What pmduct would be obtsinined if an aqueous solution of Pnwere heated at reflux? 16) Based on the reaction with sodium hydroxide, which bisulfite addition com~oundwould be used as B drinkable source far vitamin Xs? 17) Which of the following terms expresses the relationship hetween 11, I11 and IV? (a) conformers (b) enmtiomers ( c ) tautomers (d) diastereomers.
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The experiment and its emphasis on theory was appreciated by the most able students. A more effective utilization might be as an optional open-ended experiment in which the method of product identification is left to the student. Such an approach would seem ideally suited for use with the low cost nmr spectrometers that have recently become available. We wish to thank the Division of Chemical Education-Du Pont Small Grant Program for financial support of this work. We also wish t o thank Dr. H. A. Lloyd and Edward A. Sokoposki of the Laboratory of Chemistry, National Heart and Lung Institute, for providing the nmr spectra.
