Post on 05-Jan-2016
transcript
Microwave Studies of Glycerol
F.J. Lovas, and D.F Plusquellic
NIST
and
V.V. Ilyushin and R.A. Motiyenko
Institute of Radio Astronomy of NASU
Outline
Background on Studies of Polyols (for astronomy)
MW Study of Glycerol:ab Initio calculations
Prior free jet study (60 - 78 GHz)
FTMW study (9 - 26.5 GHz)
Summary
Glycerol: CH2OHCHOHCH2OH
Sweet, colorless, viscous liquid
Results from hydrolysis of fats & oils
Many applications:pharmaceuticals & cosmetics
chemical stabilizer
plasticizer coatings
moisturizer
adhesives & lubricants
Sugars and Polyols in Space
C2 sugar: “Interstellar Glycolaldehyde: The First Sugar” J.M. Hollis, F.J. Lovas, & P.R. Jewell, Ap. J. 540, L107 (2000)“Green Bank Telescope Observation of Glycolaldehyde”Hollis, Jewell, Lovas & Remijan, ApJ 613, L45 (2004)
C2 sugar alcohol: “Interstellar Antifreeze: Ethylene Glycol” Hollis, Lovas, Jewell, & Coudert, Ap. J. 571, L59 (2002)
“Ethylene glycol in comet C/1995 O1 (Hale-Bopp)” Crovisier, et al. Astron. Astrophys. 418, L35 (2004).
C3 sugars: “GBT Detection of New Interstellar Aldehydes: Propenal andPropanal” Hollis, Jewell, Lovas, Remijan & Møllendal, Ap. J.610, L21 (2004). Negative result on glyceraldehyde, C3H6O3
Sugars and Polyols in Space
C3 sugars: “1,3-Dihydroxyacetone in Sgr B2(N-LMH): The First Interstellar Ketose” S.L. Widicus Weaver & G.A. BlakeAp. J. 624, L33 (2005); erratum Ap. J. 632, Li63 (2005)
“Investigating the Limits of Chemical Complexity in Sagittarius B2(N): A Rigorous Attempt to confirm 1,3-dihydroxyacetone” Apponi, Halfen, Ziurys, Hollis, Remijan & Lovas Ap. J. 643, L29 (2006)
63 new transitions of DHA were sought but noplausible emission was observed for 97% of these
Murchison and Murray Meteorite Studies
Polyols in Meteorites by GC-MS
Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth“ Cooper, Kimmich, Belisle, Sarinana, Brabham & Garrel, Nature 414, 879 (2001).
“Murchison meteorite is generally used as the standard reference for organic compounds in Extraterrestrial material.”
Carbons Sugars Sugar Alcohols Sugar Acids
C2 --- ethylene glycol ----
C3 dihydroxyacetone glycerol glyceric acid
C4 --- Erythritol &Threitol
erythronic acid &threonic acid
C5 --- ribitol & isomers
ribonic acid &isomers
Prior Lab and Theoretical Studies
Ab Initio study of ethylene glycol and glycerol:Teppen et al. J. Mol. Struct. 314, 169 (1994).
Found 11 stable conformers for glycerol
“Free jet investigation of the rotational spectrum of glycerol” G. Maccaferri, W. Caminati, & P.G. Favero, J. Chem. Soc. FaradayTrans. 93, 4115 (1997).
Identified the 2 lowest energy conformers in the 60 – 78 GHz rangefor the normal and tri-OD species
(1) G'Gg'gg' E = 0.0 cm-1
(2) GGtg'g' E = 34.4 cm-1
(3) GGgg'g' E = 207.6 cm-1
(4) G'Gg'gt E = 240.4 cm-1
(5) GG'tg'gE = 245.9 cm-1
Five lowest energy conformers of glycerol and their relative energies from ab initio MP2 aug-cc-pVTZ basis set with zero point corrections
NIST
Mini-FTMW
Spectrometer
O p tica l Tech n o lo g y D iv is io n
Mirror-MountedHeated Reservoir Nozzle
9000 10000 11000 12000 13000 14000 15000 16000 17000 180002
3
4
5
6
7
8
9
10
Glycerol
Frequency (MHz)
Inte
nsit
y
A1
A1
A1
A1
A1A1
A2
A2
A2
A2
A2
A2
A2
A2Conformer 1
Conformer 2
Conformer 5a-type
*
*
*
C1C1
C1
B1 B1B2
B2
Parameter G'Gg'gg' (1)ab initio
MP2GGtg'g' (2)
ab initio MP2
Another Conformer like
(2)?
A (MHz) 4297.81022(11) 4327.5 0.7% 6258.33735(19) 6307.9 0.8% 6255.3793(13)
B (MHz) 3165.445328(94) 3206.1 1.3% 2283.292415(96) 2306.4 1.0% 2266.82639(79)
C (MHz) 2540.440776(96) 2583.4 1.7% 2015.899871(84) 2042.1 1.3% 2002.27853(76)
ΔJ (kHz) 1.4863(18) 0.5251(10) 0.5004(80)
Δ JK (kHz) 1.5133(52) 0.1784(32) 0.172(35)
Δ K (kHz) 2.8869(42) 7.520(16) 7.97(28)
δ J (kHz) 0.34223(93) 0.03254(34) 0.0367(45)
δ K (kHz) 0.9786(57) -0.649(14) -0.97(35)
Nlines 145 136 27
rms (MHz) 0.059 0.051 0.0022
Energy (cm-1) 0.0 34.4
Two Lowest Energy Conformers of Glycerol
C1 C1
Parameter GGgg'g' (3) ab initio MP2
A (MHz) 6224.6024(16) 6265.16 0.3%
B (MHz) 2270.72466(40) 2292.16 0.9%
C (MHz) 2011.66540(46) 2038.19 1.3%
Δ J (kHz) 0.5208(44)
Δ JK (kHz) 0.138(26)
Δ K (kHz) 8.02(37)
δ J (kHz) 0.0303(17)
δ K (kHz) -0.48(14)
Nlines 30
rms (MHz) 0.0034
Energy (cm-1) 207.6
New Conformer (3) at 207 cm-1
C1
ParameterGG'tg'g (5)
v=0GG'tg'g (5)
v=1ab initio MP2
A (MHz) 8208.24389(28) 8208.24979(28) 8295.01 1.0%
B (MHz) 1986.495283(71) 1986.495966(72) 2003.02 0.3%
C (MHz) 1712.662887(76) 1712.659143(75) 1728.10 0.9%
Δ J (kHz) 0.18335(74) 0.18249(74)
Δ JK (kHz) 2.4295(34) 2.4354(32)
Δ K (kHz) 8.406(38) 8.415(38)
δJ (kHz) 0.02318(16) 0.02363(16)
δ K (kHz) 1.146(11) 1.109(12)
E (MHz) 41.9254
Nlines 180 180
rms (MHz) 0.0025 0.0025
Energy (cm-1) 245.9
C1
Second New Conformer at 246 cm-1 with OH Tunneling
Measured and calculated dipole moments for glycerol conformers
G'Gg'gg' (1) Measured MP2 Diff. %
μa 0.780(6) D -0.81 D 3.8
μb 0.30(2) D 0.30 D 0.0
μc 1.134(4) D 1.25 D 10.2
GGtgg' (2) Measured MP2 Diff. %
μa 1.749(3) D -1.86 D 6.3
μb 0.901(2) D -1.04 D 15.5
μc 0.161(2) D -0.13 D 18.7
GGgg'g' (3) Measureda MP2 Diff. %
μa ≈1.7 D -1.61 D 5.3
μb ≈0.2 D -0.20 D 0.0
μc ≈1.7 D 2.22 D 30.3
a Estimated from intensity comparisons
GGtg'g (5) Measured MP2 Diff. %
μa 2.77(5) D -3.02 D 6.9
μb 1.47(7) D -1.20 D 18.4
μc ≈0. D 1.03 D ---
Summary
• FTMW spectrum yielded 4-5 conformers
• Ab initio calculations aided new conformer identification
• Dipole moments determined & aided assignments
• GBT data covered good candidate lines for conformers 1 & 2, but no signals observed down to 5 – 10 mK noise level