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The Vaporization Enthalpy and Vapor Pressure of Fenpropidin and Phencyclidine (PCP) at T/K = 298.15 by Correlation Gas Chromatography Chase Gobble, Barry Walker, and James S. Chickos* Department of Chemistry and Biochemistry, University of Missouri-St. Louis, St. Louis, Missouri 63121, United States S Supporting Information *

ABSTRACT: Vaporization enthalpies and liquid vapor pressures, have been evaluated at T/K = 298.15 for phencyclidine, a hallucinogen (PCP, Angel Dust) and fenpropidin, a fungicide by correlation gas chromatography. Both substances are aliphatic tertiary amines. Vapor pressures of liquid fenpropidin and subcooled liquid phencyclidine have been evaluated over a T/K = 30 temperature range. The fusion enthalpy of phencyclidine has been estimated by a group method and together with its vaporization enthalpy and subcooled liquid vapor pressure at Tfus, a sublimation enthalpy and vapor pressure of crystalline phencyclidine has also been estimated at both T/K = (Tfus and 298.15). A comparison of current results with limited amounts of both experimental and estimated data from the literature is quite good.

1. INTRODUCTION Fenpropidin (1-[3-[4-(1,1-dimethylethyl)phenyl]-2methylpropyl]piperidine) is a fungicide used to control powdery mildew, rusts, and leaf spots in cereals. It is used commercially as the racemic mixture and is thought to block plant biosynthesis of ergosterol. 1−3 Phencyclidine, (1-(1-phenyl- cyclohexyl)piperidine) also known as PCP or “Angel Dust”, was initially marketed as an anesthetic but was found to have hallucinogenic side effects.4 It is referred to as a dissociative anesthetic since users appear to be disconnected from the environment about them. It is a Schedule II substance similar to methamphetamine and cocaine and has a high propensity for abuse.4 Phencyclidine has also been used as a veterinary anesthetic or tranquillizer.4 Fenpropidin is a liquid at ambient temperatures, Tfus/K = 2085 and phencyclidine is a solid, Tfus/K = 319.7.6 This work reports the vaporization enthalpy and liquid vapor pressures of both from T/K = (283.2 to 313.2) as evaluated by correlation gas chromatography, C-GC, and compares the vapor pressure of the liquid forms to that that available on the Pesticide Properties Database,5 EPI Suite,6 and on Toxnet.7 The vapor pressures and vaporization enthalpy of phencyclidine are for the subcooled liquid. The limited amount of phencyclidine available precluded fusion enthalpy measurements. The fusion enthalpy has been estimated indirectly and in combination with it is vaporization enthalpy, a sublimation and vapor pressure of crystalline phencyclidine has been estimated. The structures of these two materials are shown in Figure 1 and those of the standards in Figure 2. The two compounds were chosen for this study in part because both are important substances for totally different reasons and structurally both are tertiary amines. Evaluation of phencyclidine emphasizes the utility of using the correlation gas chromatog© XXXX American Chemical Society

Figure 1. Structures of fenpropidin and phencyclidine (PCP).

Figure 2. Standards from top to bottom, left to right: N,Ndimethyloctylamine, N,N-dimethyldodecylamine, N,N-dimethyltetradecylamine, tributylamine, N,N-dimethylhexadecylamine, trioctylamine, and tribenzylamine.

raphy method for evaluating physical properties of substances that are commercially available only in very small quantities. The vapor pressure of phencyclidine at ambient temperatures is relevant since the material is frequently ingested by smoking or is intranasally administered.4 Information regarding the volatility of fenpropidin impacts exposure levels to users and affects levels of trace fungicide residues on consumable products.8,9 The World Received: August 31, 2015 Accepted: January 14, 2016

A

DOI: 10.1021/acs.jced.5b00737 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Origin of the Standards and Targets and Their Analysis C9H13N C12H27N C10H23N C14H31N C16H35N C17H25N C18H39N C19H3iN C21H21N C24H51N a

compound

CAS RN

supplier

mass fraction

N,N-Dimethylbenzylamine Tri-n-butylamine N,N-dimethyloctylamine N,N-dimethyldodecylamine N,N-dimethyltetradecylamine phencyclidine N,N-dimethylhexadecylamine fenpropidin tribenzylamine tri-n-octylamine

103-83-3 102-82-9 7378-99-6 112-18-5 112-75-4 77-10-1 112-69-6 067306-00-7 620-40-6 1116-76-3

Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich TCI Sigma-Aldrich Restek Sigma-Aldrich Fluka Eastmanc Sigma-Aldrich

> 0.99 0.97 0.95 > 0.95 > 0.95 RSa > 0.95 ASb

b

GC anal.

0.98 0.97 0.98+

0.98

c

Reference standard. Analytical standard. Eastman Organic Chemicals.

Table 2. Literature Vaporization Enthalpies of Some Tertiary Amines; po/Pa = 101325 ΔlgHm(Tm) compounds N,N-dimethylbenzylamine N,N-dimethyloctylamine tri-n-butylamine N,N-dimethyldodecylamine N,N-dimethyltetradecylamine N,N-dimethylhexadecylamine tribenzylamine tri-n-octylamine

kJ·mol

−1

48.9 ± 0.4 54.0 ± 0.5 58.0 ± 1.9 69.3 ± 0.3 77.3 ± 1.9 84.8 ± 1.0 92.4 ± 1.4 100.1 ± 1.4

ΔlgCpΔT

Cp(l) −1

J·mol ·K

Tm/K 308 303 298 298 298 298 298 298

248 360

−1

−1

ΔlgHm (298.15 K)

kJ·mol

kJ·mol−1 exp

ref

0.8 ± 0.2 0.5 ± 0.1

49.7 ± 0.4 54.5 ± 0.5 58.0 ± 1.9 69.3 ± 0.3 77.3 ± 1.9 84.8 ± 1.0 92.4 ± 1.4 100.1 ± 1.4

12 13 15 14 15 15 15 15

The difference in retention time between an analyte and the solvent, the adjusted retention time, ta = t − tsol, was used as a measure of the residence time of the analyte on the column; 1/ta is proportional to the vapor pressure of the analyte off the column. Plots of ln(t0/ta) against 1/T, where t0 is the reference time, 60 s, are linear and the product of the slope of the line and the gas constant measures the enthalpy of transfer of the analyte off of the column, ΔtrnHm(Tm). The vaporization enthalpy of the analyte, ΔlgHm(Tm), is related to ΔtrnHm(Tm) by eq 1 where ΔintrHm(Tm) refers to the enthalpy of interaction of the analyte with the column.11

Health Organization classifies fenpropidin as moderately hazardous.5

2. EXPERIMENTAL SECTION 2.1. Materials. Table 1 lists the source and purity of the materials used in this study. Since phencyclidine is a Schedule II substance, it is only available in solution in limited quantities. It was purchased from Restek in single milligram quantities dissolved in methanol. The sample purity evaluated by gas chromatography was >0.98 mass fraction. Fenpropidin was purchased from Fluka. The analysis of fenpropidin by gas chromatography was 0.97 mass fraction. With the exception of tribenzylamine which was also analyzed by gas chromatography, the analysis of the compounds used as standards in Table 1 are those reported by the suppliers. Since the chromatography separates the impurities, purity is not the issue as with other methods. In a separate study,10 we have found that there was no noticeable effect on the vaporization enthalpy and vapor pressure of two different materials that coeluted over the entire temperature range. 2.2. Methods. Gas chromatographic experiments were conducted over a T/K = 30 range every 5 K using an HP 5890 gas chromatograph running Chemstation. The instrument was equipped with an FID detector and run at a split ratio of approximately 100/1 using helium as the carrier. Temperature was controlled by the instrument to T/K = 0.1 and monitored by a Fluke digital thermometer. Two columns were used, a Supelco 15 m, 0.32 mm, 1.0 μm film thickness SPB-5 capillary column and a 0.25 mm, 30 m DB5 column. Column identity can be identified by the retention times, reported in the Supporting Information. On the 30 m column, the retention time of the solvent, ts/60 > 1 and on the 15 m column, ts/60 < 1. The solvents, hexanes or hexanes/CH2Cl2 were not retained by the column at the temperatures of the experiments.

Δtrn Hm(Tm) = Δl g Hm(Tm) + Δintr Hm(Tm)

(1)

Retention times were measured every T/K = 5 intervals over a T/K = 30 temperature range. Retention times are reported in the Supporting Information in order of their elution off the column (Tables S1A−S6A). Provided appropriate standards with reliable vaporization enthalpies are chosen, a second plot of ΔtrnHm(Tm) versus ΔlgHm (298.15 K) is also linear and the equation of the line combined with ΔtrnHm(Tm) of the targets can be used to evaluate the vaporization enthalpies of the latter at T/K = 298.15. Vapor pressure of the targets can also be evaluated by similar correlations. Plots of ln(p/po) versus ln(t0/ta) of the standards are also found to be linear and vapor pressures of the targets as a function of temperature can be evaluated by a similar protocol. In this work p refers to the vapor pressure and pref refers to a reference pressure, either po/Pa = 101325 or po/Pa = 1 as noted in Table 3. All vapor pressures evaluated in this work are reported in terms of po/Pa = 101325. 2.3. Vaporization Enthalpy Standards. Table 2 summarizes the vaporization enthalpies of the standards used in this work. Vaporization enthalpies for N,N-dimethylbenzylamine,12N,N-dimethyloctyl13, and N,N-dimethyldodecylamine14 are literature values evaluated by various experimental techniques. The remaining standards in Table 2 were evaluated B



Article

Table 3. Parameters of eq 2 Used as Vapor Pressure Standards; po/Pa = 101325a; T/K = 298.15 A N,N-dimethylbenzylamine N,N-dimethyloctylamine Tri-n-butylamine N,N-dimethyldodecylamine N,N-dimethyltetradecylamine N,N-dimethylhexadecylamine tri-n-octylamine tribenzylamine a

B b

13.422 14.439b 15.181 40.49339 17.399 18.368 20.362 18.361

ln(po/Pa) 298.15 K

C b

5892.0 6498.8b 6965.9 17623.5 9337.0 10270.3 12148 11175.4

0 0 0 135.268 0 0 0 0

−0.168c

T/K range

ln(p/po)

ref

288−328 284−323 283−313 283−314 283−313 283−313 283−313 283−313

−6.34 −7.36 −8.18 −11.69 −13.92 −16.08 −20.38 −19.12

12 13 15 14 15 15 15 15

Unless noted otherwise. bCalculated from the vapor pressure data reported. cpo = 1 Pa.

uncertainties, as defined by the “Guide to the Expression of Uncertainty in Measurement”.

by correlation gas chromatography using these and other tertiary amines as standards.15 2.4. Vapor Pressure Standards. The compounds chosen as vaporization enthalpy standards also served as vapor pressure standards. The vapor pressures were all calculated using eq 2. The reference pressure for N,N-dimethyldodecylamine, pref = po/ Pa = 1, while for the remaining compounds in Table 3, pref = po/ Pa = 101325. The constants for most compounds reported in Table 3 are valid over the temperature range, T/K = (283−313). The vapor pressure values for N,N-dimethylbenzylamine required an extrapolation of T/K = 5 to lower temperature. ln(p/pref ) = A − B /(C + T /K)

3. RESULTS 3.1. Vaporization Enthalpies. Table 4 summarizes two set of results for phencyclidine using slightly different standards and a set of results for fenpropidin. Results from duplicate runs are summarized in the Supporting Information. A second set of correlations are reported for phencyclidine since the retention times of the standards used in the first set did not bracket the target. The equations of the lines are given at the bottom of the table, eqs 5−7. Similar tables and equations for the duplicate runs are provided in the Supporting Information. All results are summarized in Table 5 and are within experimental error of each other. The last column in Table 5 reports the average value evaluated for each compound. The uncertainty is also an average of each standard deviation. Vaporization enthalpies at T/K = 298.15 of 77.6 ± 2.1 and 80.9 ± 1.6 kJ·mol−1 have been evaluated for phencyclidine and fenpropidin, respectively. 3.2. Vapor Pressures. Correlations between ln(p/po) with ln(t0/ta) of the standards at T/K = 298.15 are reported in Table 6. Values for (t0/ta) were evaluated for each compound using both duplicate runs, averaged, and then ln(t0/ta)avg of the standards were correlated with the corresponding values of ln(p/po). Equations 8−10 summarize the results of each set of correlations at T/K = 298.15. The resulting correlation coefficient associated with each equation provides a measure of the linearity of each correlation. These equations in combination with ln(t0/ta)avg of the targets were then used to evaluate their corresponding ln(p/ po) values. Each correlation was then repeated at T/K = 5 intervals over the applicable range of the constants provided in Table 3, T/K = (283.2 to 313.2). Correlation coefficients, r2, obtained at all temperatures in this temperature range exceeded 0.99. Table 7 summarizes the slopes and intercepts resulting from plots of ln(p/po) versus 1/T for both phencyclidine and fenpropidin. Vaporization enthalpies calculated from the vapor pressures over the temperature range T/K = (283.2 to 313.2) are reported in the fourth column. The vaporization enthalpies compare very favorably to those reported in Table 5. Vapor pressures and their uncertainties for the targets reported in column 5 of Table 7 are from the slopes and intercepts of columns 2 and 3; those in the last column of Table 7 are calculated from the last column of Table 6. The vapor pressures calculated from the slopes and intercept reported in Table 7 are very similar to those reported in Table 6; their uncertainties are somewhat smaller. Vaporization enthalpies and vapor pressures evaluated from correlations of the standards for each set of runs are included in the Supporting Information, Table S7.

(2)

2.5. Temperature Adjustments. The vaporization enthalpies of all but two of the standards are available at T/K = 298.15. In estimation of the sublimation enthalpy of phencyclidine at T/K = 298.15 as described below, it was also necessary to adjust both the vaporization and sublimation enthalpies for temperature. The following two equations, 3 and 4, were used for these purposes. Equation 3 was used to adjust the vaporization enthalpy and eq 4 was used to adjust the sublimation enthalpy.The terms Tf and Ti refer to the final and initial temperature and Cp(l) and Cp(cr) refer to the heat capacity of liquid and solid phase, respectively.16 Values for Cp(l) and Cp(cr) were both estimated by group additivity.17 Δl g Hm(Tf )/(kJ·mol−1) = Δl g Hm(Ti)/kJ·mol−1 + [10.58 + 0.26·Cp(l) /(J·mol−1·K−1)][Tf − Ti]/(1000 K)

(3)

Δcr g Hm(Tf )/(kJ·mol−1) = Δcr g Hm(Ti)/kJ·mol−1 + [0.75 + 0.15·Cp(cr) /(J·mol−1·K−1)][Tf − Ti]/(1000 K)

(4)

2.6. Uncertainties. All slopes and intercepts reported below were calculated by linear regression. Uncertainties associated with results derived by combination of two or more experimental values were derived as (u12 + u22 + ...)0.5. All uncertainties refer to one standard deviation unless noted otherwise. Uncertainties evaluated from logarithmic terms are reported as the average of the two uncertainties calculated. The uncertainty associated with the Cp(l) term in eq 3 is 16 J·mol−1·K−1, while the uncertainty associated with eq 4 is 30% of the temperature adjustment. The heat capacity values used for each adjustment are provided in the tables below. Uncertainties associated with the slopes and intercepts of plots of ln(t0/ta) vs 1/T/K are provided in the Supporting Information. The standard deviations reported in the tables of experimental data are equivalent to the standard C



Article

Table 4. Vaporization Enthalpy Results for Phencyclidine and Fenpropidin; Uncertainties are 1 Standard Deviation, po = 101325 Pa −slope

ΔHtrn (464 K)

Run 1

T/K

intercept

N,N-dimethylbenzylamine N,N-dimethyloctylamine tri-n-butylamine N,N-dimethyldodecylamine N,N-dimethylhexadecylamine phencyclidine

4134.4 4919.2 4999.5 6335.0 8084.2 7236.9 −slope

9.811 11.409 11.208 12.791 14.952 13.037

Run 3

T/K

intercept

tri-n-butylamine N,N-dimethyldodecylamine N,N-dimethylhexadecylamine phencyclidine tri-n-octylamine

4778.1 6033.4 7696.7 6941.6 9293.5 −slope

10.733 12.148 14.130 12.409 16.071

Run 5

T/K

N,N-dimethyldodecylamine N,N-dimethyltetradecylamine N,N-dimethylhexadecylamine fenpropidin tri-n-octylamine tribenzylamine

−5883.9 −6629.8 −7431.1 −7025.6 −8904.9 −8172.3 Run 1:

−1

kJ·mol

34.37 40.90 41.56 52.67 67.21 60.16 ΔHtrn (489 K) −1

kJ·mol

ΔlgHm (298.15 K) −1

kJ·mol

ΔlgHm (298.15 K) kJ·mol−1(calc)

(lit)

49.7 ± 0.4 54.5 ± 0.5 58.0 ± 1.9 69.3 ± 0.3 84.8 ± 1.0 ΔlgHm (298.15 K)

49.2 ± 2.8 56.3 ± 3.0 57.0 ± 3.0 69.0 ± 3.4 84.8 ± 3.9 77.2 ± 3.7 ΔlgHm (298.15 K)

kJ·mol−1 (lit)

kJ·mol−1(calc)

58.0 ± 1.9 69.3 ± 0.3 84.8 ± 1.0

39.72 50.16 63.99 57.71 77.26 ΔHtrn (498 K)

100.1 ± 1.4 ΔlgHm (298.15 K)

57.8 ± 0.7 69.5 ± 0.8 85.0 ± 0.9 78.0 ± 0.8 99.9 ± 1.0 ΔlgHm (298.15 K)

intercept

kJ·mol−1

kJ·mol−1 (lit)

kJ·mol−1(calc)

12.429 13.251 14.175 13.170 15.915 14.336

48.92 55.12 61.78 58.41 74.03 67.94

69.3 ± 0.3 77.3 ± 3.0 84.8 ± 1.0

69.4 ± 1.1 76.9 ± 1.2 85.0 ± 1.2 81.0 ± 1.2 99.9 ± 1.4 92.5 ± 1.3

100.1 ± 1.4 92.4 ± 1.4

Δl g Hm(298.15 K)/kJ·mol−1 = (1.085 ± 0.047)ΔHtrn(489 K) + (11.90 ± 2.30)

r 2 = 0.9943

(5)

Run 3:


r 2 = 0.9998

(6)

Run 5:


r 2 = 0.9996

(7)

Table 5. A Summary of the Vaporization Enthalpy of the Targets and Standards in kJ·mol−1 at T/K = 298.15; po = 101325 Pa Targets phencyclidine fenpropidin Standards N,N-dimethylbenzylamine N,N-dimethyloctylamine tri-n-butylamine N,N-dimethyldodecylamine N,N-dimethyltetradecylamine N,N-dimethylhexadecylamine tri-n-octylamine tribenzylamine a

Run 1

Run 2

Run 3

Run 4

77.2 ± 3.7

77.2 ± 3.4

78.0 ± 0.8

77.8 ± 0.6

49.2 ± 2.8 56.3 ± 3.0 57.0 ± 3.0 69.0 ± 3.4

49.3 ± 2.6 56.1 ± 2.7 57.0 ± 2.8 69.1 ± 3.1

84.8 ± 3.9

84.8 ± 3.6

57.8 ± 0.7 69.5 ± 0.8

57.9 ± 0.5 69.4 ± 0.5

85.0 ± 0.9 99.9 ± 1.0

85.0 ± 0.6 100.0 ± 0.7

Run 5

Run 6

Averagea

81.0 ± 1.2

80.8 ± 2.0

77.6 ± 2.1 80.9 ± 1.6

69.3 ± 1.8 76.9 ± 1.9 85.3 ± 2.0 99.7 ± 2.2 92.6 ± 2.1

49.3 ± 2.7 56.2 ± 2.9 57.4 ± 1.8 69.3 ± 1.8 76.9 ± 1.6 85.0 ± 2.0 99.9 ± 1.3 92.6 ± 1.7

69.4 ± 1.1 76.9 ± 1.2 85.0 ± 1.2 99.9 ± 1.4 92.5 ± 1.3

The uncertainty is an average of the standard deviations reported in columns 2−7.

phencyclidine evaluated in this work, p/Pa = (0.03 ± 0.006), compares to an estimated value of p/Pa = 0.04.6 Vapor pressures for phencyclidine are for the subcooled liquid; agreement with this work is quite good. The vapor pressure for fenpropidin at T/ K = 298.15 has been reported as p/Pa = 0.017.5 Agreement with this work, p/Pa = (0.016 ± 0.004), is within experimental error. A reference to the original literature for fenpropidin is not available.

Table 8 summarizes both the vaporization enthalpies and vapor pressures at T/K = 298.15 evaluated in this work. The vaporization enthalpies for both targets and standards are the mean values reported in Table 5; vapor pressures are average values from the last column of Table 7. Experimental vaporization enthalpies for the two target molecules are not presently available. At T/K = 298.15, the vapor pressure of D



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Table 6. Correlation of ln(p/po) with ln(to/ta) for Runs 1−6 at T/K = 298.15; po = 101325a −slope/K

intercept

4134.4 −4102.4 4919.2 −4861.2 4999.5 −4962.2 6335.0 −6296.6 8084.2 8062.8 7236.9 −7197.8

9.811 9.746 11.409 11.287 11.208 11.132 12.791 12.713 14.952 14.911 13.037 12.958

−4778.1 −4811.4 −6033.4 −6020.2 −7696.7 −7653.1 −6941.6 −6899.4 −9293.5 −9224.1

10.733 10.812 12.148 12.131 14.13 14.05 12.409 12.331 16.071 15.938

−5883.9 −5915.1 −6629.8 −6672.2 −7431.1 −7510.5 −8172.3 −8234.3 −8904.9 −8940.9 −7025.6 −7058.5 Run 1/2:

12.429 12.49 13.251 13.334 14.175 14.332 14.336 14.458 15.915 15.986 13.17 13.235

Run 1/2 N,N-dimethylbenzylamine N,N-dimethyloctylamine tri-n-butylamine N,N-dimethyldodecylamine N,N-dimethylhexadecylamine phencyclidine Run 3/4 tri-n-butylamine N,N-dimethyldodecylamine N,N-dimethylhexadecylamine phencyclidine trioctylamine Run 5/6 N,N-dimethyldodecylamine N,N-dimethyltetradecylamine N,N-dimethylhexadecylamine tribenzylamine tri-n-octylamine fenpropidin

ln(t0/ta)avg

ln(p/po)lit

ln(p/po)calca

−4.034

−6.34

−6.29 ± 0.16

−5.053

−7.36

−7.52 ± 0.16

−5.535

−8.18

−8.11 ± 0.17

−8.431

−11.69

−11.62 ± 0.21

−12.147

−16.08

−16.11 ± 0.26

−11.209

−14.99 ± 0.24

−5.309

−8.18

−8.2 ± 0.07

−8.074

−11.65

−11.65 ± 0.08

−11.651

−16.08

−16.12 ± 0.10

−10.841

−15.11 ± 0.09

−15.049

−20.38

−20.37 ± 0.11

−7.327

−11.69

−11.68 ± 0.22

−9.015

−13.92

−13.86 ± 0.23

−10.802

−16.08

−16.18 ± 0.25

−13.116

−19.12

−19.18 ± 0.28

−13.977

−20.38

−20.29 ± 0.29

−10.417

ln(p /po ) = (1.213 ± 0.018) ln(to/ta) − (1.397 ± 0.138);

−15.68 ± 0.25

r 2 = 0.9993

(8)

r 2 = 0.9999

(9)

r 2 = 0.9995

(10)

Run 3/4:

ln(p /po ) = (1.249 ± 0.006) ln(to/ta) − (1.565 ± 0.065); Run 5/6:

ln(p /po ) = (1.296 ± 0.016) ln(to/ta) − (2.185 ± 0.182); a

The uncertainty is 1 standard deviation.

Table 7. Vaporization Enthalpies (po = 101325 Pa) and Vapor Pressures Evaluated from Correlation of ln(to/ta)avg with ln(p/po)lit. Uncertainties, 1 Standard Deviation Run

−slope/K

intercept

ΔlgHm(298.15 K)a kJ·mol−1

102·p298.15 K/Pab

102·p298.15 K/Pac

1/2, phencyclidine 3/4, phencyclidine 5/6, fenpropidin

9288.8 ± 10.7 9373.2 ± 6.8 9759.6 ± 8.2

16.169 ± 0.036 16.330 ± 0.022 17.055 ± 0.028

77.2 ± 0.1 77.9 ± 0.1 81.1 ± 0.1

3.1 ± 0.2 2.8 ± 0.1 1.6 ± 0.001

3.1 ± 0.7 2.8 ± 0.5 1.6 ± 0.4

a Calculated the product of the slope (column 2) and the gas constant. bCalculated the product of the slope and intercept; uncertainty is an average of 1 standard deviation. cCalculated from the last column of Table 6; uncertainty is 1 standard deviation (average value).

3.3. Sublimation Enthalpy. As noted above, phencyclidine is a solid at room temperature melting at Tfus/K = 319.65. As a Schedule II drug, commercial sample sizes available currently precluded us from experimentally measuring its fusion enthalpy.

However, a fairly accurate group additivity method has been developed for estimating the total phase change entropy from T/ K = (0 to Tfus), ΔStpce.19 Assuming there are no significant solid− solid phase transitions occurring in phencyclidine below T/K = E



Article

Table 8. A Summary of the Vaporization Enthalpies (po = 101325 pa) and Liquid Vapor Pressures at T/K = 298.15 Evaluated in This Work. Uncertainties Are 1 Standard Deviation ΔlgHm(298 K)/kJ·mol−1 this work Targets phencyclidine fenpropidin Standards N,N-dimethylbenzylamine N,N-dimethyloctylamine tri-n-butylamine N,N-dimethyldodecylamine N,N-dimethyl tetradecylamine N,N-dimethylhexadecylamine tri-n-octylamine tribenzylamine a

102·p298.15 K/Pa avg

lit.

77.6 ± 2.1 80.9 ± 1.6 49.3 ± 2.7 56.2 ± 2.9 57.4 ± 1.8 69.3 ± 1.8 76.9 ± 1.6 85.0 ± 2.0 99.9 ± 1.3 92.6 ± 1.7

49.7 ± 0.4 54.5 ± 0.5 58.0 ± 1.9 69.3 ± 0.3 77.3 ± 3.0 84.8 ± 1.0 100.1 ± 1.4 92.4 ± 1.4

ref

3.0 ± 0.6 1.6 ± 0.4

4.0a 1.71b

6 5

18800 ± 2900 5470 ± 900 2920 ± 360 89 ± 16 9.6 ± 2.3 1.0 ± 0.2 0.015 ± 0.0016 0.05 ± 0.01

17900b 6300b 2830c 85b 9.2c 1.1c 0.14c, 0.13d 0.05c, 0.26a

12 13 15 14 15 15 15, 18 15, 6

Estimated vapor pressure of the subcooled liquid. bExperimental vapor pressure. cEvaluated previously by correlation. dExtrapolated value, ref 18.

298.15, ΔStpce in combination with the fusion temperature, Tfus·ΔStpce, can provide a reasonable value for ΔcrlHm(Tfus). Applying the protocol developed, a value, ΔStpce = (62.5 ± 13) J· mol−1·K−1 is calculated.19 Details describing the estimation are provided in the Supporting Information. The product, Tfus·ΔStpce, results in a fusion enthalpy of (20 ± 6) kJ·mol−1. The vaporization enthalpy of phencyclidine adjusted to the fusion temperature using eq 3 is summarized in Table 9.

pressure of phencyclidine is calculated from the slopes and intercepts of runs 1/2 and 3/4 from Table 7 and then averaged, a vapor pressure of p/Pa = (0.25 ± 0.05) at this temperature results. Substitution of the appropriate values into eq 11 results in a vapor pressure of the solid of p/Pa = (0.019 ± 0.007) at T/K = 298.15. For comparison, the EPI Suite predicts a vapor pressure of p/Pa = 0.026 at this temperature, the last entry in Table 9.6 ln(p(298.15) /po ) = [{ΔHsub(Tfus) + (Δcr g CpΔT )

Table 9. Vaporization and Estimated Sublimation Enthalpies for Phencyclidine and Their Temperature Adjustments, (po = 101325 Pa); Estimated Vapor Pressure of Solid Phencyclidine. Uncertainties Are 1 Standard Deviation ΔlgHm(298.15 K) kJ·mol−1 Tfus/K ΔlgCp/J·mol−1·K−1 10−3·ΔlgCp·ΔT/kJ·mol−1 ΔlgHm(Tfus)/kJ·mol−1 ΔStpce/J·mol−1·K−1 ΔcrlHm(Tfus)a/kJ·mol−1 ΔlgHm(Tfus)/kJ·mol−1 ΔcrgHm(Tfus)a/kJ·mol−1 ΔcrgCp/J·mol−1·K−1 10−3·ΔcrgCp·ΔT/kJ·mol−1 ΔcrgHm(298.15K)a/kJ·mol−1 102·p298/Pa twa,b/litc a

102·p298.15 K/Pa lit

/2}/J·mol−1][K/Tfus − 1/298.15)] /[(J· K−1· mol−1)/R] + ln(p(T fus) /po ) (11)

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77.6 ± 2.1 319.65 429.9 −2.63 ± 0.3 75.0 ± 2.2 62.5 ± 13 20 ± 5.9 75.0 ± 2.2 95.0 ± 6.3 349.3 1.1 ± 0.3 96.1 ± 6.3 1.9 ± 0.07/2.6

SUMMARY Vaporization enthalpies of (77.6 ± 2.1) and (80.9 ± 1.6) kJ· mol−1 and liquid vapor pressures, p/Pa = (0.03 ± 0.006) and (0.016 ± 0.004) have been evaluated at T/K = 298.15 for phencyclidine and fenpropidin, respectively, by correlation gas chromatography. Experimental vaporization enthalpies are not available. An experiment vapor pressure of p/Pa = 0.0171 has previously been reported for fenpropidin.13 A sublimation enthalpy of (96.1 ± 6.3) kJ·mol−1 at T/K = 298.15 has been estimated for phencyclidine by combining the vaporization enthalpy evaluated at Tfus with an estimated fusion enthalpy and adjusting the sum back to T/K = 298.15. An estimated vapor pressure for solid phencyclidine at T/K = 298.15 was calculated by evaluating the vapor pressure of liquid phencyclidine at the approximate temperature at which solid is in equilibrium with liquid, Tfus, and in combination with the sublimation enthalpy adjusting the results back to T/K = 298.15. The estimated value of p/Pa = (0.019 ± 0.07) from this work compares with a literature estimation of p/Pa = 0.026.5

Estimated. bThis work. cReference 6.

Combined with the estimated fusion enthalpy of (20 ± 5.9) kJ· mol−1, a value of (95.0 ± 6.3) kJ·mol−1 is calculated for the sublimation enthalpy at Tfus. Adjusted to T/K = 298.15 using eq 4 results in a sublimation enthalpy of (96.1 ± 6.3) kJ·mol−1. The temperature adjustment is also summarized in Table 9. 3.4. Sublimation Vapor Pressure. Using experimental fusion and vaporization enthalpies and vapor pressures at Tfus, eq 11 has been shown to reproduce experimental vapor pressures of a variety of different organic solids within a factor of 3.20 To evaluate the vapor pressure of solid phencyclidine, in addition to the sublimation enthalpy at the triple point temperature, the vapor pressure of the solid at this temperature is also required. The vapor pressure of liquid phencyclidine is basically within the accessible temperature range of the fusion temperature. If the the triple point is approximated as Tfus = 319.7 and the vapor

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.5b00737. Tables of experimental retention times, results of duplicate runs, results from correlations of ln(t0/ta) with ln(p/po) and total phase change entropy calculations described in the text (PDF) F



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Article

(20) Chickos, J. S. Sublimation Vapor Pressures as Evaluated by Correlation-Gas Chromatography. J. Chem. Eng. Data 2010, 55, 1558− 1563.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) http://www.pesticides.gov.uk/Resources/CRD/ACP/067_ fenpropidin.pdf (accessed 5/08/15). (2) http://sitem.herts.ac.uk/aeru/bpdb/Reports/307.htm (accessed 5/08/15). (3) Baloch, R. I.; Mercer, E. I.; Wiggins, T. E.; Baldwin, B. C. Inhibition of ergosterol biosynthesis in saccharomyces cerevisiae and Ustilagomaydis by tridemorph, fenpropimorph and fenpropidin. Phytochemistry 1984, 23, 2219−2226. (4) http://www.nhtsa.gov/people/injury/research/job185drugs/ phencyclidine.htm and references cited (accessed 5/14/15). (5) Pesticide Properties Data Base: http://sitem.herts.ac.uk/aeru/ ppdb/en/Reports/307.htm (accessed 7/07/15). (6) Estimation Program Interface EPI Suite Version 4.11 (Nov. 2012); available at http://www.epa.gov/opptintr/exposure/pubs/episuite.htm (accessed 7/23/2013). (7) http://toxnet.nlm.nih.gov/cgi-bin/sis/search2 (accessed 11/03/ 2015). (8) Zhao, H.; Xue, J.; Jiang, N.; Peng, W.; Liu, F. Dissipation and residue of fenpropidin in wheat and soil under field conditions. Ecotoxicol. Environ. Saf. 2012, 77, 52−56. (9) http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id= PC38489 (accessed 11/03/2015). (10) Gobble, C.; Chickos, J. S. A Comparison of Results by Correlation Gas Chromatography with Other Gas Chromatographic Retention Time Methods. The Effects of Retention Time Coincidence On Vaporization Enthalpy and Vapor Pressure. J. Chem. Eng. Data 2015, 60, 2739−2748. (11) Peacock, L. A.; Fuchs, R. Enthalpy of Vaporization Measurements by Gas Chromatography. J. Am. Chem. Soc. 1977, 99, 5524−5525. (12) Verevkin, S. P. Strain Effects in Phenyl-Substituted Methanes. Geminal Interaction between Phenyl and the Electron-Releasing Substituents in Benzylamines and Benzyl Alcohols. J. Chem. Eng. Data 1999, 44, 1245−1251. (13) Verevkin, S. P. Thermochemistry of amines: experimental standard molar enthalpies of formation of some aliphatic and aromatic amines. J. Chem. Thermodyn. 1997, 29, 891−899. (14) Fulem, M.; Ruzicka, K.; Ruzicka, V.; Hulicius, E.; Simecek, T.; Pangrac, J.; Rushworth, S. A.; Smith, L. M. Measurement of vapour pressure of In-based metalorganics for MOVPE. J. Cryst. Growth 2004, 272, 42−46. (15) Gobble, C.; Vikman, J.; Chickos, J. S. Evaluation of the Vaporization Enthalpies and Liquid Vapor Pressures of (R)-Deprenyl, (S)-Benzphetamine, Alverine and a Series of Aliphatic Tertiary Amines by Correlation Gas at T/K = 298.15 Chromatography. J. Chem. Eng. Data 2014, 59, 2551−2562. (16) Acree, W., Jr.; Chickos, J. S. Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2009. J. Phys. Chem. Ref. Data 2010, 39, 1−942. (17) Chickos, J. S.; Hesse, D. G.; Liebman, J. F. A Group Additivity Approach for the Estimation of Heat Capacities of Organic Liquids and Solids. Struct. Chem. 1993, 4, 261−268. (18) Steele, W. V.; Chirico, R. D.; Knipmeyer, S. E.; Nguyen, A.; Smith, N. K.; Tasker, I. R. Thermodynamic Properties and Ideal-Gas Enthalpies of Formation for Cyclohexene, Phthalan (2,5-Dihydrobenzo-3,4-furan), Isoxazole, Octylamine, Dioctylamine, Trioctylamine, Phenyl Isocyanate, and 1,4,5,6-Tetrahydropyrimidine. J. Chem. Eng. Data 1996, 41, 1269− 1284. (19) Chickos, J. S.; Acree, W. E., Jr. Total phase change entropies and enthalpies. An update on fusion enthalpies and their estimation. Thermochim. Acta 2009, 495, 5−13. G


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