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)
Why study propargyl alcohol?
(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
c) Multifunctional molecule , like phenylacetylene
Phac-H2ORef1
Both groups can act as
H-bond donor/acceptor
Phac-H2SRef2
Offers many possibilities for H-bonding !
1. M. Goswami and E. Arunan, Phys. Chem. Chem. Phys., 2011, 13, 14153–14162
2. M. Goswami and E. Arunan, J. Mol. Spectrosc., 2011 ,268,1-2,147-156
Propargyl alcohol (monomer)
 Due to internal motion of –OH group, this molecule can mainly
exist as two conformers: Gauche and trans
1.8
1.6
Cis
1.2
trans
-1
Energy (kcalmol )
1.4
Relaxed scan at
mp2/6-311+(d,p)
1.0
0.8
-1
0.6
1 kcalmol
0.4
0.2
Gauche
0.0
-0.2
100
200
300
400
500
600
D(C2C3O1H4)
700
800
900
1000
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.
2.
3.
4.
5.
Eizi Hirota, Journal of Molecular Spectroscopy 26, 335-350 (1968)
K. Bolton, N.L. Owen, J. Sheridan, Nature 217 (1968) 164.
J.C. Pearson , B.J. Drouin , Journal of Molecular Spectroscopy 234 (2005) 149–156
F. Scappini et al. CPL, 1975, 33(3), 499-501.
Harald Møllendal et al. J. Phys. Chem. A 2010, 114, 5537–5543
Ar   Propargyl alcohol complex
2.8A0
At MP2/6-311+G(3df,2p)
3.8A0
oxygen-hydrogen-Argon angle=145.20
Argon-pi bond-carbon angle = 74.50
COHAr dihedral angle = 25.90
oxygen-hydrogen-Argon angle=138.80
COHAr dihedral angle ~ 00
Ab-initio calculated rotational constants
and dipole-moment components
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
Fitted constants
Constants
Lower set
Upper set
Line centre
A/MHz
B/MHz
C/MHz
DJ/kHz
DJK/kHz
DK/kHz
d1/kHz
d2/kHz
# transitions
rms deviation /kHz
4346.1695(20)
1617.15059(41)
1245.42035(28)
7.3141(43)
61.552(33)
-55.30(43)
-2.1765(30)
-0.7138(11)
45
4.7
4346.1785(22)
1617.15664(47)
1245.42070(32)
7.3166(49)
61.569(38)
-55.00(48)
-2.1729(34)
-0.7150(13)
45
5.3
4346.1735(11)
1617.15334(24)
1245.42047(18)
7.3132(27)
61.552(21)
-55.17(24)
-2.1738(18)
-0.71468(73)
50
3.1
D. Mani, E. Arunan, ChemPhysChem 14, 754 (2013)
Nature of interactions: AIM analysis
Ar g-PA
Ar t-PA

Ar methanol

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
View 1
At MP2/6-311+G(3df, 2p)
View 2
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
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
2
2
2
3
2
2
3
3
3
3
3
4
3
4
5
3
2
2
2
4
4
4
4
4
4
1
0
1
0
1
1
1
0
2
2
1
0
1
0
1
1
2
2
2
2
2
3
3
1
0
2
2
1
3
2
1
3
3
2
1
2
4
3
4
4
2
1
0
0
3
2
2
1
4
4
J K-1 K+1
1
1
1
2
1
1
2
2
2
2
2
3
2
3
4
2
1
1
1
3
3
3
3
3
3
1
0
1
1
0
0
1
0
2
2
1
1
0
1
2
0
1
1
1
2
2
3
3
1
0
1
1
0
1
1
1
2
2
1
0
1
2
2
3
3
2
0
0
1
2
1
1
0
3
3
Frequency
(MHz)
Residue
(MHz)
Type
4525.0904
4550.2612
4576.2612
5601.3099
5696.4442
5773.2026
6787.2685
6824.2441
6825.9070
6827.5363
6864.0172
7834.1436
7933.4491
7987.6514
8012.6465
8086.9612
8090.3430
8090.7486
8116.3340
9100.6989
9104.7685
9101.7826
9101.8119
9049.0136
9096.8586
0.0026
0.0003
0.0011
0.0078
-0.0001
-0.0013
0.0018
-0.0010
-0.0010
-0.0005
0.0014
-0.0013
-0.0011
-0.0022
-0.0007
0.0024
0.0014
-0.0004
-0.0023
0.0002
0.0032
-0.0050
0.0008
0.0003
0.0000
a
a
a
c
b
c
a
a
a
a
a
c
b
b
b
c
b
c
b
a
a
a
a
a
a
4
6
5
5
3
3
4
3
4
5
5
5
5
5
5
5
5
5
5
4
6
4
3
3
3
5
1
1
0
0
2
2
1
2
1
1
0
2
4
4
2
3
3
1
1
2
0
2
3
3
3
1
3
6
5
5
2
1
3
1
4
5
5
4
1
2
3
3
2
4
5
3
6
2
1
0
1
4
3
5
4
4
2
2
3
2
3
4
4
4
4
4
4
4
4
4
4
3
5
3
2
2
2
4
1
2
1
1
1
1
0
1
0
1
0
2
4
4
2
3
3
1
0
1
1
1
2
2
2
0
2
3
3
4
1
1
3
2
3
4
4
3
0
1
2
2
1
3
4
2
5
3
0
0
1
4
9151.3160
9810.4390
10050.4868
10306.2977
10339.9928
10342.0246
10414.0309
10418.7855
10158.2185
11310.1924
11367.6588
11375.0490
11376.7770
11376.7770
11383.1636
11377.2647
11377.3477
11438.0039
12371.5539
12576.6710
12632.3367
12736.2806
12746.5296
12746.5296
12746.9447
12755.1770
-0.0009
0.0031
0.0000
-0.0014
0.0033
-0.0011
0.0003
0.0002
0.0002
0.0000
0.0000
-0.0019
0.0009
0.0012
0.0007
-0.0004
0.0006
0.0011
0.0018
-0.0015
0.0027
-0.0033
-0.0011
-0.0050
0.0066
0.0023
a
b
c
b
b
c
c
b
b
a
a
a
a
a
a
a
a
a
b
b
b
b
b
c
c
c
Fitted Constants
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
D. Mani, E. Arunan, manuscript under preparation
Isotopic substitution: 1
H-16 as Deuterium
Calculated constants
A /MHz
2299.9
B /MHz
1148.4
C
1119.6
/MHz
Observed signals
J K-1 K+1
2
3
3
3
3
4
4
4
4
4
4
4
5
5
5
5
5
5
5
1
1
0
1
1
0
1
0
2
2
1
1
0
1
0
2
2
1
1
1
3
3
2
3
4
4
4
3
2
3
4
5
5
5
4
3
4
5
J K-1 K+1
1
2
2
2
2
3
3
3
3
3
3
3
4
4
4
4
4
4
4
0
1
0
1
0
1
1
0
2
2
1
0
1
1
0
2
2
1
0
1
2
2
1
2
3
3
3
2
1
2
3
4
4
4
3
2
3
4
Frequency
(MHz)
obs -cal
(MHz)
5748.995
6749.679
6797.907
6851.091
7864.025
7994.144
8998.544
9060.247
9067.065
9074.314
9133.683
10064.66
10315.15
11246.55
11319.56
11332.59
11347.03
11415.34
12250.95
-0.0007
-0.0055
-0.0005
0.0018
0.0043
0.0013
-0.0008
-0.0095
0.014
0.008
-0.0103
-0.0021
0.0041
-0.0021
0.004
-0.0098
-0.0068
0.0065
0.0038
Fitted constants
A /MHz
2297.8207(52)
B /MHz
1150.4122(13)
C
1116.6032(14)
/MHz
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
Isotopic substitution: 2
H-8 as Deuterium
Calculated constants
A /MHz
2304.9
B /MHz
1146.9
C /MHz
1124.3
Observed signals
J K-1 K+1
3
3
3
4
4
4
4
4
4
5
5
5
5
5
1
0
1
1
0
2
2
1
1
1
0
2
2
1
3
3
2
4
4
3
2
3
4
5
5
4
3
4
J K-1 K+1
2
2
2
3
3
3
3
3
3
4
4
4
4
4
1
0
1
1
0
2
2
1
0
1
0
2
2
1
2
2
1
3
3
2
1
2
3
4
4
3
2
3
Frequency
(MHz)
obs -cal
(MHz)
6801.5120
6828.0980
6856.1370
9068.2370
9102.9418
9104.9295
9107.0125
9141.0600
10178.2245
11334.5930
11376.7613
11380.5950
11384.7490
11425.5832
0.0030
-0.0050
0.0006
-0.0006
-0.0001
-0.0009
0.0013
0.0021
0.0000
0.0007
0.0001
-0.0001
-0.0012
-0.0001
Fitted constants
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
D. Mani, E. Arunan, manuscript under preparation
Isotopic substitution: 3
H-16 and H-8 as Deuterium
Calculated constants
A /MHz
2283.2
B /MHz
1144.6
C /MHz
1119.3
Observed signals
J K-1 K+1
3
3
3
3
3
2
4
4
4
4
4
4
5
5
5
5
5
1
0
2
2
1
2
0
1
0
2
2
1
0
1
0
2
1
3
3
2
1
2
1
4
4
4
3
2
3
5
5
5
3
4
J K-1 K+1
2
2
2
2
2
1
3
3
3
3
3
3
4
4
4
4
4
1
0
2
2
1
1
1
1
0
2
2
1
1
1
0
2
1
2
2
1
0
1
1
3
3
3
2
1
2
4
4
4
2
3
Frequency
(MHz)
obs -cal
(MHz)
6764.8930
6802.1560
6803.9150
6805.6330
6842.3510
7992.9680
7994.1390
9019.1860
9067.3170
9071.3630
9075.6600
9122.4200
10306.3045
11272.8660
11330.5803
11346.9195
11401.8630
-0.0016
-0.0008
0.0000
-0.0010
-0.0094
0.0025
-0.7342
0.0162
-0.0018
-0.0005
0.0053
-0.0051
0.0074
-0.0012
-0.0135
-0.0024
0.0051
Fitted constants
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
#transitions
8.7
17
D. Mani, E. Arunan, manuscript under preparation
AIM analysis
O-H
O-H  O
C-H  
Contact
ρ(r) in a.u.
2ρ(r) in a.u.
OHO
0.0233
0.0921
OH
0.0156
0.0501
CH
0.0058
0.0166
(H2O)2
H2OC2H2
H2OC2H4
(CH3OH)2
(C2H2)2
CH4C2H2
Contact
OHO
OH
CH
Complex
ρ(r) in a.u. 2ρ(r) in a.u.
PA-dimer
0.0233
0.0921
Water-dimer
0.0215
0.0960
Methanol-dimer
0.0256
0.1018
PA-dimer
0.0156
0.0501
Acetylene..water
0.0100
0.0324
Ethylene…water
0.0100
0.0291
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”.
Methanol ESP surface
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
Microwave spectra of complexes like CH4HF/HCl/HCN and CH4  H2O
show that the hydrogen of HX molecule points towards the tetrahedral face of
methane.
Microwave spectra of CH4ClF 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 ?
H2OCH3OH complex
H2OCH3OH complex was optimized taking initial geometry in which oxygen
of water points towards the CH3 face of methanol.
3.167 Å
b.c.p.
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.
Is this a general interaction ?
Similar interaction with other molecules
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.
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-HO, O-H  , C-H  
interactions.
 54 lines remain unassigned which could be due to higher PA-clusters.
My group





Acknowledgements
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.