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0.5 hr. Methylcyclopropyl ketone (8.4 g.) in 25 ml. of ether was then added and stirring was continued for 1 hr. more. The reaction wa3 mixed with 150 ml. of water and the ether layer was then separated and dried. Distillation yielded 1.5 g. of XIII, b.p. 50" (43 mm.). The infrared spectrum showed a carbon-carbon stretching band at 6.22 p and a cyclopropyl band at 9.51 p . Other bands were a t 3. 25, 3.41, 3.72, 4.77, 5.23, 7.01, 7.48, 8.28, 8.64, 9.51, and 12.50 H . Compound XI11 was separated into its cis and trans isomers using preparative V.P.C. {Ucon oil column). The n.m.r. spectrum of one isomer consisted of a multiplet for cyclopropyl CH2 centered a t T 9.37 (relative area 4), a methyl singlet at 7 8.60 (relative area 3), and a broad peak for the vinyl proton at T 4.28 (relative area I). The n.1n.r. spectrum of the other isomer likewise consisted of a multiplet centered at T 9.49, a singlet at T 8.36, and a broad peak at T 4.25 (relative areas 4:3:1). No attempt was made to assign which isomer was cis and which was trans. The infrared spectrum of each isomer was indistinguishable from the mixture of the two.Anal. Caicd. for CsHgCl: C, 61.78; H, 7.73; C1, 30.49. Found: C, 61.71; H,7.87; C1,30.26. 7,7-Dichlorobicyclo [4.1 .O] hept-Zene (XXI).-Potassium tbutoxide (33.7 g.) was slurried in 500 ml. of dry n-pentane containing 46.2 g . of cyclohexa-1,3-diene. The mixture was cooled in an ice-salt bath, and chloroform (34.6 9.) was added dropmise over a 2-hr. period, the temperature being kept below 0". The reaction mixture was then warmed to room temperature and wa3hed with dilute hydrochloric acid. The organic layer was separated, washed with water, dried, and distilled. Compound XXI (18.5 9.) was obtained as a colorless, sweetsmelling liquid, b.p. 65" (5.5 mm.). The infrared spectrum of XXI showed banda at 6.00 (C=C stretch) and 9.53 , u (cyclo-propyl). Other bands were a t 3.42, 6.20, 7.05, 7.22, 7.71, 8.18, 10.25, 11.89, 12.20, and 13.65 p . The n.m.r. spectrum of this material consists of multiplets centered at T 8.78 (cyclopropyl CH), 7.82 (methylene CHt), 7.02 (allylic CH:), and 3.98 (vinyl). All four groups of signals have approximately the same arefts. Anal. Calcd. for C7HeClt: C, 51.53; H, 4.91; C1, 43.56. Found: C,51.53; H,4.88; C1,43.58.4-Dichloromethylenecyclohexene (XXII) .-Compound XXI was passed through a 1-m. Vycor tube packed with glass wool and held at 275", 18 times at a rate of 30 ml./hr. The product showed only two major peaks in the V.P.C. These two materials were separated by preparative v.p.c. on a Ucon oil column. One was shown, by comparison with an authentic sample, to be benzyl chloride. The other was shown to be compound XXII. The infrared spectrum of XXII consisted of a carbon-carbon stretching absorption at 6.32 p and other bands a t 3. 41, 6.33, 7.14,7.42,7.68,8.01,8.24,9.53,10.18,and12.20p. Then.m.r. spectrum of XXII consisted of a multiplet for methylene protons centered at T 8.15 (relative area 3) and an olefinic proton signal centered at T 4.33 (relative area 1).Anal. Ca...

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Single-channel potassium currents from lobster axon membranes were studied in planar bilayers made from monolayers. Channel-opening events are grouped by time, forming bursts with an average duration of 4.5 ms. The mean open time at 0 mV is 1.8 ms. The frequency of bursts is voltage dependent, increasing e-fold per 12-16 mV. At sufficiently high positive voltages, channels inactivate. Measured from reversal potentials, channels discriminate against Na+ by a permeability ratio PNa/PK of 1:30. The channel is blocked by tetraethylammonium and nonyltrimethylammonium in a voltage-dependent manner and at concentrations similar to those used in whole-axon experiments. Voltage-dependent block by Cs+ suggests that more than one ion may occupy the channel simultaneously. The kinetics and selectivity of this channel suggest that purified axolemma contains active K+ channels that are likely to participate in delayed rectification in the lobster axon membrane.