Rotational spectra of propargyl alcohol dimer: O-H O, O-H , C-H interactions Devendra Mani and...
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Transcript of Rotational spectra of propargyl alcohol dimer: O-H O, O-H , C-H interactions Devendra Mani and...
Rotational spectra of propargyl alcohol dimer: O-H O, O-H , C-H interactions
Devendra Mani and E. Arunan Department of Inorganic & Physical Chemistry,
Indian Institute of Science, Bangalore, India.
Pulsed Nozzle Fourier Transform Microwave spectrometer (PNFTMW)
(a) Molecule of Astro-physical interest
– Vinyl alcohol (C2H4O) was found in 2001.
– Propanal (C3H6O) was found in 2006.
– Will propargyl alcohol (C3H4O) be found ?
(b) Combustion
Propargyl radical is considered to be precursor in soot formation.
C3H3 + C3H3 C6H6 or C6H5 +H
Why study propargyl alcohol?
Both groups can act as H-bond donor/acceptor
c) Multifunctional molecule , like phenylacetylene
Offers many possibilities for H-bonding !
Phac-H2ORef1
1. M. Goswami and E. Arunan, Phys. Chem. Chem. Phys., 2011, 13, 14153–141622. M. Goswami and E. Arunan, J. Mol. Spectrosc., 2011 ,268,1-2,147-156
Phac-H2SRef2
Propargyl alcohol (monomer) Due to internal motion of –OH group, this molecule can mainly exist as two conformers: Gauche and trans
100 200 300 400 500 600 700 800 900 1000-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
En
erg
y (
kc
alm
ol-1
)
D(C2C3O1H4)
1 kcalmol-1
Gauche
Cistrans
Relaxed scan at mp2/6-311+(d,p)
Rotational Spectrum • Many groups in 1960s worked on propargyl alcohol1,2.
• Recently in 2005, Pearson et al. revisited the rotational spectrum of this molecule3.
• Only gauche conformer could be observed and no spectroscopic signature for
trans form was present.
• Tunneling frequencies between gauche conformers for OH species and OD species have been determined to be 652.38GHz and 213.48 GHz respectively.
• For propargyl mercaptan (HC≡CCH2SH)4 and propargyl selenol (HC≡CCH2SeH)5 also only gauche conformer was observed!
• Can trans form be observed in molecular beams ?
• Can it be stabilized via complex formation with e.g., Ar/H2O? 1. Eizi Hirota, Journal of Molecular Spectroscopy 26, 335-350 (1968)2. K. Bolton, N.L. Owen, J. Sheridan, Nature 217 (1968) 164.3. J.C. Pearson , B.J. Drouin , Journal of Molecular Spectroscopy 234 (2005) 149–1564. F. Scappini et al. CPL, 1975, 33(3), 499-501. 5. Harald Møllendal et al. J. Phys. Chem. A 2010, 114, 5537–5543
Ar Propargyl alcohol complex
2.8A0
3.8A0
oxygen-hydrogen-Argon angle=145.20
Argon-pi bond-carbon angle = 74.50
COHAr dihedral angle = 25.90
At MP2/6-311+G(3df,2p)
oxygen-hydrogen-Argon angle=138.80
COHAr dihedral angle ~ 00
Ar g-PA Ar t-PA
A/MHz 4312 13563
B/MHz 1684 932
C/MHz 1281 863
μa 0.9 D 1.8 D
μb 1.1 D 1.3 D
μc 0.8 D 0.0 D
Ab-initio calculated rotational constants and dipole-moment components
Constants Lower set Upper set Line centreA/MHz 4346.1695(20) 4346.1785(22) 4346.1735(11)B/MHz 1617.15059(41) 1617.15664(47) 1617.15334(24)C/MHz 1245.42035(28) 1245.42070(32) 1245.42047(18)DJ/kHz 7.3141(43) 7.3166(49) 7.3132(27)
DJK/kHz 61.552(33) 61.569(38) 61.552(21)
DK/kHz -55.30(43) -55.00(48) -55.17(24)
d1/kHz -2.1765(30) -2.1729(34) -2.1738(18)
d2/kHz -0.7138(11) -0.7150(13) -0.71468(73)# transitions 45 45 50
rms deviation /kHz 4.7 5.3 3.1
D. Mani, E. Arunan, ChemPhysChem 14, 754 (2013)
Fitted constants
Ar g-PA
Ar methanol
Ar t-PA
Nature of interactions: AIM analysis
22 unassigned lines which depend only on PA concentration!!
None of these lines corresponds to the monomer spectra!
Can it be due to higher clusters of propargyl alcohol , dimer or may be trimer?
Propargyl alcohol dimer
A/MHz 2286
B/MHz 1234
C/MHz 1209
μa /D 1.8
μb /D 1.5
μc /D 2.1
E/kJ.mol-1 31.8
At MP2/6-311+G(3df, 2p)
View 1 View 2
He used as carrier gas
~6% of which was flown through a bubbler containing propargyl alcohol
Dependence of the signals was checked by turning off the flow through PA sample.
Already observed signals were used as the initial guess and other signals were searched according to the dimer predictions.
Total 51 transitions could be fitted to the experimental uncertainty.
Observed signals for PA-dimer
J K-1 K+1 J K-1 K+1 Frequency
(MHz) Residue(MHz) Type
2 1 2 1 1 1 4525.0904 0.0026 a 2 0 2 1 0 1 4550.2612 0.0003 a 2 1 1 1 1 0 4576.2612 0.0011 a 3 0 3 2 1 1 5601.3099 0.0078 c 2 1 2 1 0 1 5696.4442 -0.0001 b 2 1 1 1 0 1 5773.2026 -0.0013 c 3 1 3 2 1 2 6787.2685 0.0018 a 3 0 3 2 0 2 6824.2441 -0.0010 a 3 2 2 2 2 1 6825.9070 -0.0010 a 3 2 1 2 2 0 6827.5363 -0.0005 a 3 1 2 2 1 1 6864.0172 0.0014 a 4 0 4 3 1 2 7834.1436 -0.0013 c 3 1 3 2 0 2 7933.4491 -0.0011 b 4 0 4 3 1 3 7987.6514 -0.0022 b 5 1 4 4 2 3 8012.6465 -0.0007 b 3 1 2 2 0 2 8086.9612 0.0024 c 2 2 1 1 1 0 8090.3430 0.0014 b 2 2 0 1 1 0 8090.7486 -0.0004 c 2 2 0 1 1 1 8116.3340 -0.0023 b 4 2 3 3 2 2 9100.6989 0.0002 a 4 2 2 3 2 1 9104.7685 0.0032 a 4 3 2 3 3 1 9101.7826 -0.0050 a 4 3 1 3 3 0 9101.8119 0.0008 a 4 1 4 3 1 3 9049.0136 0.0003 a 4 0 4 3 0 3 9096.8586 0.0000 a
4 1 3 3 1 2 9151.3160 -0.0009 a 6 1 6 5 2 3 9810.4390 0.0031 b 5 0 5 4 1 3 10050.4868 0.0000 c 5 0 5 4 1 4 10306.2977 -0.0014 b 3 2 2 2 1 1 10339.9928 0.0033 b 3 2 1 2 1 1 10342.0246 -0.0011 c 4 1 3 3 0 3 10414.0309 0.0003 c 3 2 1 2 1 2 10418.7855 0.0002 b 4 1 4 3 0 3 10158.2185 0.0002 b 5 1 5 4 1 4 11310.1924 0.0000 a 5 0 5 4 0 4 11367.6588 0.0000 a 5 2 4 4 2 3 11375.0490 -0.0019 a 5 4 1 4 4 0 11376.7770 0.0009 a 5 4 2 4 4 1 11376.7770 0.0012 a 5 2 3 4 2 2 11383.1636 0.0007 a 5 3 3 4 3 2 11377.2647 -0.0004 a 5 3 2 4 3 1 11377.3477 0.0006 a 5 1 4 4 1 3 11438.0039 0.0011 a 5 1 5 4 0 4 12371.5539 0.0018 b 4 2 3 3 1 2 12576.6710 -0.0015 b 6 0 6 5 1 5 12632.3367 0.0027 b 4 2 2 3 1 3 12736.2806 -0.0033 b 3 3 1 2 2 0 12746.5296 -0.0011 b 3 3 0 2 2 0 12746.5296 -0.0050 c 3 3 1 2 2 1 12746.9447 0.0066 c 5 1 4 4 0 4 12755.1770 0.0023 c
A /MHz 2321.83350(42)
B /MHz 1150.47741(21)
C /MHz 1124.88979(16)
DJ /kHz 1.8422(31)
DJK /kHz 0.375(11)
DK /kHz -0.982(40)
d1 /kHz -0.0457(27)
d2 /kHz -0.1498(22)
s/kHz 2.5
# transitions 51
Fitted Constants
D. Mani, E. Arunan, manuscript under preparation
H-16 as Deuterium
Isotopic substitution: 1
A /MHz 2299.9
B /MHz 1148.4
C /MHz 1119.6
Calculated constants
J K-1 K+1 J K-1 K+1 Frequency
(MHz)obs -cal(MHz)
2 1 1 1 0 1 5748.995 -0.0007 3 1 3 2 1 2 6749.679 -0.0055 3 0 3 2 0 2 6797.907 -0.0005 3 1 2 2 1 1 6851.091 0.0018 3 1 3 2 0 2 7864.025 0.0043 4 0 4 3 1 3 7994.144 0.0013 4 1 4 3 1 3 8998.544 -0.0008 4 0 4 3 0 3 9060.247 -0.0095 4 2 3 3 2 2 9067.065 0.014 4 2 2 3 2 1 9074.314 0.008 4 1 3 3 1 2 9133.683 -0.0103 4 1 4 3 0 3 10064.66 -0.0021 5 0 5 4 1 4 10315.15 0.0041 5 1 5 4 1 4 11246.55 -0.0021 5 0 5 4 0 4 11319.56 0.004 5 2 4 4 2 3 11332.59 -0.0098 5 2 3 4 2 2 11347.03 -0.0068 5 1 4 4 1 3 11415.34 0.0065 5 1 5 4 0 4 12250.95 0.0038
Observed signals
Fitted constants
A /MHz 2297.8207(52)
B /MHz 1150.4122(13)
C /MHz 1116.6032(14) DJ /kHz 1.826(20) DJK /kHz 0.40(14) DK /kHz -1.000 d1 /kHz -0.059(17) d2 /kHz -0.174(10)
s/kHz 7.9
#transitions 19
D. Mani, E. Arunan, manuscript under preparation
H-8 as Deuterium
A /MHz 2304.9
B /MHz 1146.9
C /MHz 1124.3
Isotopic substitution: 2
Calculated constants
J K-1 K+1 J K-1 K+1 Frequency
(MHz)obs -cal(MHz)
3 1 3 2 1 2 6801.5120 0.0030 3 0 3 2 0 2 6828.0980 -0.0050 3 1 2 2 1 1 6856.1370 0.0006 4 1 4 3 1 3 9068.2370 -0.0006 4 0 4 3 0 3 9102.9418 -0.0001 4 2 3 3 2 2 9104.9295 -0.0009 4 2 2 3 2 1 9107.0125 0.0013 4 1 3 3 1 2 9141.0600 0.0021 4 1 4 3 0 3 10178.2245 0.0000 5 1 5 4 1 4 11334.5930 0.0007 5 0 5 4 0 4 11376.7613 0.0001 5 2 4 4 2 3 11380.5950 -0.0001 5 2 3 4 2 2 11384.7490 -0.0012 5 1 4 4 1 3 11425.5832 -0.0001
Observed signals
A /MHz 2301.8767(51)
B /MHz 1147.29807(87)
C /MHz 1129.08541(85)
DJ /kHz 1.7851(72)
DJK /kHz 0.233(51)
DK /kHz -1.000
d1 /kHz -0.042(10)
d2 /kHz -0.1130(33)
s/kHz 2.5
#transitions 14
Fitted constants
D. Mani, E. Arunan, manuscript under preparation
Isotopic substitution: 3
H-16 and H-8 as Deuterium
A /MHz 2283.2
B /MHz 1144.6
C /MHz 1119.3
Calculated constants
J K-1 K+1 J K-1 K+1 Frequency
(MHz)obs -cal(MHz)
3 1 3 2 1 2 6764.8930 -0.0016 3 0 3 2 0 2 6802.1560 -0.0008 3 2 2 2 2 1 6803.9150 0.0000 3 2 1 2 2 0 6805.6330 -0.0010 3 1 2 2 1 1 6842.3510 -0.0094 2 2 1 1 1 1 7992.9680 0.0025 4 0 4 3 1 3 7994.1390 -0.7342 4 1 4 3 1 3 9019.1860 0.0162 4 0 4 3 0 3 9067.3170 -0.0018 4 2 3 3 2 2 9071.3630 -0.0005 4 2 2 3 2 1 9075.6600 0.0053 4 1 3 3 1 2 9122.4200 -0.0051 5 0 5 4 1 4 10306.3045 0.0074 5 1 5 4 1 4 11272.8660 -0.0012 5 0 5 4 0 4 11330.5803 -0.0135 5 2 3 4 2 2 11346.9195 -0.0024 5 1 4 4 1 3 11401.8630 0.0051
Observed signals
A /MHz 2282.0237(32)
B /MHz 1146.9285(19)
C /MHz 1121.1011(21)
DJ /kHz 1.764(25)
DJK /kHz -0.21(18)
DK /kHz -1.0000
d1 /kHz -0.054(25)
d2 /kHz -0.118(17)
s/kHz 8.7
#transitions 17
Fitted constants
D. Mani, E. Arunan, manuscript under preparation
AIM analysis
O-H O C-H p
O-Hp
Contact ρ(r) in a.u. 2ρ(r) in a.u.
OHO 0.0233 0.0921
OHp 0.0156 0.0501
CHp 0.0058 0.0166
(H2O)2
H2OC2H2(C2H2)2
CH4C2H2H2OC2H4
(CH3OH)2
Contact Complex ρ(r) in a.u. 2ρ(r) in a.u.
OHO
PA-dimer 0.0233 0.0921
Water-dimer 0.0215 0.0960
Methanol-dimer 0.0256 0.1018
OHp
PA-dimer 0.0156 0.0501
Acetylene..water 0.0100 0.0324
Ethylene…water 0.0100 0.0291
CHp
PA-dimer 0.0058 0.0166
methane_acetylene 0.0042 0.0109
acetylene_dimer 0.0064 0.0178
D. Mani, E. Arunan, manuscript under preparation
Other face of methanol: The “carbon bond”.
ESP value at face centre +50.2 kJ.mol-1
Tetrahedral face of methane has a –ve centre!
ESP value at face centre = -7.5 kJ.mol-1
Methanol ESP surface
Microwave spectra of complexes like CH4HF/HCl/HCN and CH4 H2O show that the hydrogen of HX molecule points towards the tetrahedral face of methane.
Microwave spectra of CH4ClF complex shows that the Cl points towards the tetrahedral face of methane.
AIM studies confirm the presence of interactions between carbon of methane and hydrogen of HX molecules as well as Cl of ClF leading to the formation of a hydrogen bond and halogen bond respectively.
What are the bonding properties of the CH3 face of methanol ?
Being electropositive can this face interact with electron rich centres of molecules like water ?
H2OCH3OH complex was optimized taking initial geometry in which oxygen of water points towards the CH3 face of methanol.
3.167 Å
BSSE corrected interaction energy = 4.2 kJ mol-1
Electron density ρ(r), at intermolecular b.c.p. = 0.0050 a.u.
Laplacian of electron density 2ρ(r) at intermolecular b.c.p. = 0.0248 a.u.
H2OCH3OH complex
b.c.p.
Is this a general interaction ?
Optimized geometries for (a) H2O•••CH3OH, (b) H2S•••CH3OH, (c) HF•••CH3OH, (d) HCl•••CH3OH, (e)HBr•••CH3OH, (f) LiF•••CH3OH, (g) LiCl•••CH3OH, (h) LiBr•••CH3OH, (i) ClF•••CH3OH, (j) H3N•••CH3OH, (k) H3P•••CH3OH complexes.
Similar interaction with other molecules
D.Mani, E. Arunan, PCCP, DOI: 10.1039/C3CP51658J
Nomenclature ?
D.Mani, E. Arunan, PCCP, DOI: 10.1039/C3CP51658J
Conclusions
Rotational spectra of PA-dimer and its three deuterated isotopologues has been observed and fitted by a semirigid rotor asymmetric top Hamiltonian.
Observed rotational constants are close to the Ab-initio predicted structure.
AIM calculations show that in the dimer two monomer entities are in a three point contact having O-HO, O-H p , C-H p interactions.
54 lines remain unassigned which could be due to higher PA-clusters.
Acknowledgements My group
Department of Science and Technology, India. Indo-French Centre of Pure and Applied Research. Council of Industrial and Scientific Research, India. Royal Society of Chemistry (PCCP) for travel grant. Indian Institute of Science, Bangalore, India.
Thank you
for your kind attention.