1. CVEN 5424 Environmental Organic Chemistry Lecture 4 – Vapor Pressure Estimation

2. Announcements Reading  Chapter 4, Vapor pressure Problem sets PS 1 due today PS 2 out today Office hours – next week (because of travel) Monday 9-10 am Tuesday 11:30 am-1 pm Office hours – semester Tuesday 11:30 am-1:00 pm Wednesday 9-10 am

3. Announcements Room SEEC C326 (RASEI Fellows Conf Rm) – this week SEEC S298 – rest of the semester, starting Jan 26 Lectures lecture Tues Jan 26 no lecture Thur Jan 28 double up Tues Jan 26, 8:30 am or 11:30 am double up Tues Feb 2, 8:30 am or 11:30 am

4. Vapor Pressure

5.  Clayperon I  For the phase transition 1  2,   12 H is the change in molar enthalpy  measures intermolecular attraction   12 V is the change in molar volume  measures randomness Benoît Paul Émile Clapeyron 1799-1864

6. Vapor Pressure solid liquid gas 1 2 3

7. Vapor Pressure  Solid-liquid   12 H =  fus H  fus H is large   12 V =  fus V  fus V is small   fus H /T  fus V is very large; so is dp/dT solid liquid gas 1 1

8. Vapor Pressure  Liquid-gas   12 H =  vap H  vap H is large (  vap H >  fus H)   12 V =  vap V  vap V is large (  vap V >>  fus V)   vap H /T  vap V is small; so is dp/dT solid liquid gas 2 2

9. Vapor Pressure  Solid-gas   12 H =  sub H  sub H is very large (=  fus H +  vap H)   12 V =  sub V  sub V is large (  fus V +  vap V) ~  sub V   sub H/T  sub V is “medium”; so is dp/dT solid liquid gas 3 3

10. Vapor Pressure Hypothetical liquids –“subcooled liquid” –hypothetically –hypothetically not having to pay melting costs to get solid to vaporize –will be important for determining vaporization of organic compound from water solid liquid gas TmTm

11. Vapor Pressure Hypothetical liquids –“superheated liquid” –hypothetical –hypothetical vapor pressure of a liquid above its boiling point solid liquid gas 1 atm TbTb

12. Vapor Pressure  Clayperon II  Enthalpy  breaking bonds in condensed phase  essentially no bonds formed in vapor phase  Entropy  increase in randomness in gas phase  bonding results in orientation in condensed phases

13. Vapor Pressure  Clayperon II  Enthalpy  van der Waals  varying electron distribution: dipole-induced dipole, dipole- dipole  relevant for all compounds  characteristic of apolar or nonpolar compounds  major contributor to  12 H

14. Vapor Pressure  Clayperon II  Enthalpy  monopolar  electron donor OR electron acceptor character  donors: ether (-C-O-C-), keto (>C=O)  acceptors: aromatic ring with electronegative substituents  minor contributor to  12 H; a few kJ mol -1

15. Vapor Pressure  Clayperon II  Enthalpy  bipolar  electron donor-acceptor, or hydrogen bonding, character  hydroxyl (-OH), carboxyl (-COOH)  amino (-NH 2 )  sulfhydryl (-SH)  significant contributor to  12 H; 10-20 kJ mol -1  monopolar and bipolar = polar

16. Vapor Pressure  Clayperon II  Entropy  solid  liquid  static in solid; some interactions in liquid  liquid  gas  some orientation in liquid; none in gas  molecular characteristics  allows translation – all molecules  allows rotation – non-symmetric molecules  allows flexing – molecules with chains

17. Vapor Pressure alkane T b (  C) log p* (bar)  vap,sub H (kJ mol -1 ) T  vap,sub S (J mol -1 ) methane, CH 4 -164.02.458.625.6 ethane, C 2 H 6 -88.61.6115.724.8 propane, C 3 H 8 -42.10.9819.525.0 butane, C 4 H 10 -0.50.4023.225.3 pentane, C 5 H 12 36.1-0.1729.127.7 hexane, C 6 H 14 69.0-0.7030.125.2 heptane, C 7 H 16 98.4-1.2135.530.0 octane, C 8 H 18 125.7-1.7441.032.8 nonane, C 9 H 20 150.8-2.2442.732.0 decane, C 10 H 22 174.1-2.7642.530.0 hexadecane, C 16 H 34 287.0-5.7353.932.7

18. Vapor Pressure 25°C

19. Vapor Pressure

20.  What explains the decrease in vapor pressure for alkanes of increasing chain length? A. hydrogen bonding increases with chain length B. van der Waals forces increase with chain length C. electron donor-acceptor (polar) forces increase with chain length D. increase in entropy increases with chain length E. both B and D

21. Vapor Pressure  What explains the decrease in vapor pressure for alkanes of increasing chain length? A. hydrogen bonding increases with chain length B. van der Waals forces increase with chain length C. electron donor-acceptor (polar) forces increase with chain length D. increase in entropy increases with chain length E. both B and D

22. Vapor Pressure  What explains the decrease in vapor pressure for alkanes of increasing chain length? A. hydrogen bonding increases with chain length B. van der Waals forces increase with chain length C. electron donor-acceptor (polar) forces increase with chain length D. increase in entropy increases with chain length E. both B and D entropy does increase with chain length, but an increase in entropy favors an increase in vapor pressure

23. Vapor Pressure compoundstructure T b (  C)  vap H (T b ) (kJ mol -1 )  (D) benzene8030.80 chlorobenzene13236.51.54 1,2-dichlorobenzene18044.02.50 1,3-dichlorobenzene17344.11.72 1,4-dichlorobenzene17444.20 1,2,3-trichlorobenzene21947.41.64 1,2,4-trichlorobenzene21449.50.81 1,3,5-trichlorobenzene20850.30 1,2,3,4-tetrachlorobenzene25456.71.90 1,2,3,5-tetrachlorobenzene24651.10.65 1,2,4,5-tetrachlorobenzene24352.00 pentachlorobenzene27762.10.88 hexachlorobenzene32268.70

24. Vapor Pressure  What is another name for this compound, 1,4- dichlorobenzene? A. chlorobenzene B. p-chlorobenzene C. p-dichlorobenzene D. p-dichlorobenzoic acid E. Paracide

25. Vapor Pressure  What is another name for this compound, 1,4- dichlorobenzene? A. chlorobenzene B. p-chlorobenzene C. p-dichlorobenzene D. p-dichlorobenzoic acid E. Paracide

26. Vapor Pressure

30.  What kind of interaction is responsible for the increase in boiling point and enthalpy of vaporization in the series of benzene, chlorobenzene, and o-dichlorobenzene? A. van der Waals B. polar (electron donor-acceptor) C. hydrogen bonding

31. Vapor Pressure  What kind of interaction is responsible for the increase in boiling point and enthalpy of vaporization in the series of benzene, chlorobenzene, and o-dichlorobenzene? A. van der Waals B. polar (electron donor-acceptor) C. hydrogen bonding

32. Vapor Pressure Data Vapor pressure from data (e.g., CRC Handbook) ln p (bar) 1/T (K -1 ) higher T lower TmTm solid liquid subcooled liquid

33. ln p (bar) 1/T (K -1 ) TmTm p iL *  vap H/R  sub H/R p iL * p iS *  sub H =  vap H +  fus H

35. Vapor Pressure Data  Example  determine the vapor pressure of tetrachloroethene at 25  C using vapor pressure data from the CRC*  T m = -19  C = 254 K  T b = 121  C = 394 K *or some other source of P-T data T (  C) p L,S (mm Hg) -20.6s1 13.810 40.140 61.3100 100.0400 120.8760

36. Vapor Pressure Data  Example  determine the vapor pressure of tetrachloroethene at 25  C using vapor pressure data from the CRC*  T m = -19  C = 254 K  T b = 121  C = 394 K *or some other source of P-T data T (  C) p L,S (mm Hg) -20.6s1 13.810 40.140 61.3100 100.0400 120.8760

37. Vapor Pressure Data  Example  determine the vapor pressure of tetrachloroethene at 25  C using vapor pressure data from the CRC*  T m = -19  C = 254 K  T b = 121  C = 394 K *or some other source of P-T data T (  C) p L,S (mm Hg) -20.6s1 13.810 40.140 61.3100 100.0400 120.8760

38.  Example  ln p vs. 1/T Vapor Pressure Data T (C) T (K) 1/T (1/K) ln p (bar) p (bar) p (mm Hg) 13.82870.00348-4.317620.013310 40.1313.30.00319-2.931330.053340 61.3334.50.00299-2.015040.1333100 373.20.00268-0.628740.5333400 120.83940.002540.0131121.0132760

39. Vapor Pressure Data  Example  enthalpy of vaporization

40. Vapor Pressure Data  Example  vapor pressure at 25  C

41. Vapor Pressure Data  Example  vapor pressure at 25  C

42. Vapor Pressure Data  Example  vapor pressure at 25  C

43. Vapor Pressure Estimation  Estimating vapor pressure of a liquid – where we are headed:

44. Vapor Pressure Estimation  Estimating vapor pressure of a solid – where we are headed:

45. Next Lecture  Vapor Pressure  Aqueous Solubility  start reading Chapter 5