trifluoromethyl oxirane and 2vinyloxirane two candidates for chiral analysis via noncovalent chiral tagging Mark D Marshall Helen O Leung Desmond Acha Kevin Wang Olivia ID: 630229
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Slide1
The microwave spectra and molecular structures of 2-(trifluoromethyl)-oxirane and 2-vinyloxirane, two candidates for chiral analysis via noncovalent chiral tagging
Mark D. Marshall, Helen O. Leung, Desmond Acha, Kevin Wang, Olivia Febles, Alexandra GomezDepartment of ChemistryAmherst College
Supported by the National Science FoundationSlide2
Noncovalent chiral taggingSlide3
Requirements for chiral tagEasily available in enantiopure formSmall, chiral molecule
Easy to introduce into free-jet expansionFunctionalized for noncovalent interactionsSimple rotational spectrumMinimal isotopic dilution (13C, 18O helpful)
No hyperfine
No internal rotation
Spectroscopically
characterized
Structure determined
2-(
trifluoromethyl
)-
oxirane (TFO)
2-vinyloxirane (VO)Slide4
Experimental methodsChirped pulse Fourier transform microwave spectrometer6.1 – 18.1 GHz (TFO)5.6 - 18.1 GHz (VO)
1% TFO in argon or liquid VO entrained in argon is expanded through two pulsed valves with 0.8 mm nozzleSpectra obtained as 4 GHz portions, 20 W power, 4 s chirpTen 10-s FIDs per gas pulse
618,000 – 900,000 FIDs averaged
200 kHz FWHM
Spectra analyzed using
Kisiel’s
AABS package in conjunction with Pickett’s SPFIT/SPCAT
Photo courtesy of
Jessica Mueller,
Amherst CollegeSlide5
TFO spectrum - overviewc-type transitions(purple & blue)
b-type transitions
(green &
teal
)
a
-type transitions
(red)
μ
a
= 1.49 D
μ
b
= 1.82 D
μ
c
= 1.17 DSlide6
TFO spectrum – 500 MHz portionSlide7
TFO – spectroscopic constants
CH2CH(CF3)O13CH2CH(CF
3
)O
CH
2
13
CH(CF
3
)O
CH2CH(
13CF3)OCH2CH(CF
3
)
18
O
A / MHz
4595.69375(43)
4575.75379(79)
4577.75383(99)
4596.08287(86)
4554.9283(13)
B / MHz
2177.88275(21)
2144.71422(50)
2168.34203(71)
2174.86702(52)
2120.91207(89)
C / MHz
2063.53764(21)
2029.81723(50)
2058.54030(70)
2060.83065(56)
2004.49405(82)
J
/
10
-3
MHz
0.2531(22)
0.235(10)
0.263(14)
0.2370(92)
0.283(30)
JK
/
10
-3
MHz
1.5833(19)
1.549(19)
1.493(20)
1.554(16)
1.586(49)
K
/
10
-3
MHz
−0.9442(88)
−0.926(42)
−0.908(45)
−0.916(43)
−1.50(18)
J
/
10
-3
MHz
0.02160(11)
0.0221(26)
0.0239(20)
0.0249(16)
0.0225(16)
K
/
10
-3
MHz
−0.8504(57)
−0.79(10)
−0.57(12)
−0.559(86)
[−0.8504
]
J range
0 – 16
0 – 10
0 – 10
0 – 10
0 – 10
K
a
range
0 – 8
0 – 4
0 – 4
0 – 4
0 – 3
rms
/ kHz
8.43
8.44
10.93
9.89
6.38Slide8
TFO - structureKisiel’s STRFIT used to fit A, B, C of 5 isotopologues to 6 structural parameters2 bond lengths and one angle in ring–CF3 carbon located relative to O and plane of ring
All other parameters fixed at ab initio valuesrms = 0.00070 u Å2 and well-behaved correlationsEVAL used to calculate chemically relevant parameters
1.4309(4
)
Å
1.46(1)
Å
59.7(8)
o
1.44(1)
Å
1.498(4)
Å
113.4(9)
oSlide9
VO spectrum - overviewμa = 0.81 Dμb
= 1.78 Dμc = 0.41 DSlide10
VO spectrum – 1200 MHz portionSlide11
VO – spectroscopic constants
C4H6O 13CH2CHOC2H3
CH
2
13
CHOC
2
H
3
CH2CHO13CHCH
2
CH2CHOCH13CH2 C2H
3
18
OC
2
H
3
A / MHz
17367.2865(62)
17093.0919(24)
17261.4319(68)
17272.3215(18)
17359.0192(24)
16774.5386(54)
B / MHz
3138.1862(16)
3097.70172(49)
3134.0039(16)
3116.09328(41)
3045.06444(53)
3072.07730(90)
C / MHz
3043.6985(23)
2997.25591(65)
3042.9673(18)
3025.74048(48)
2956.24829(52)
2963.91544(72)
J
/
10
-3
MHz
0.4697(72
)
[0.470]
[0.470]
[0.470]
[0.470]
[0.470]
JK
/
10
-3
MHz
10.098(81
)
[10.10]
[10.10]
[10.10]
[10.10]
[10.10]
K
/
10
-3
MHz
10.08(34
)
[10.08]
[10.08]
[10.08]
[10.08]
[10.08]
J
/
10
-3
MHz
0.0096(13)
[0.0096]
[0.0096]
[0.0096]
[0.0096]
[0.0096]
K
/
10
-3
MHz
-11.14(78
)
[ -11.14]
[ -11.14]
[ -11.14]
[ -11.14]
[ -11.14]
RMS /
kHz
5.155
6.145
4.691
4.068
5.692
7.127
Highest
J
13
7
6
4
10
9
Highest
K
a
3
2
2
2
4
1Slide12
VO - structure
1.436(3) Å1.439(7) Å
1.474(6) Å
61.7(4)
o
1.477(4) Å
1.338(2) Å
115.9(7)
o
122.9(3)
o
Kisiel’s
STRFIT used to fit A, B, C of 6 isotopologues to 9 structural parameters
2 bond lengths and one angle in ring
C=C bond length, C–C=C angle, and C–C=C–C dihedral [–150.3(8)°]
–
C
=CH
2
carbon located relative to O and plane of ring
All other parameters fixed at
ab
initio
values
rms
= 0.00025 u
Å
2
and well-behaved correlations
EVAL used to calculate
chemically relevant parametersSlide13
Ar-TFO – spectroscopic constants
Ar−CH2CH(CF3)OAr−13CH2CH(CF3)O
Ar−CH
2
13
CH(CF
3
)O
Ar−CH
2CH(13CF3)O
A / MHz
3105.06577(36)
3060.66880(21)
3104.15793(27)
3104.09772(25)
B / MHz
600.48925(11)
600.21588(11)
600.49728(13)
598.50592(13)
C / MHz
571.12061(11)
569.76461(11)
571.15084(13)
569.28788(13)
J
/
10
-3
MHz
0.66395(30)
0.65736(24)
0.66297(29)
0.65993(28)
JK
/
10
-3
MHz
−2.0995(20)
−2.1322(24)
−2.1026(33)
−2.1150(31)
K
/
10
-3
MHz
31.812(15)
31.773(22)
31.885(30)
31.867(29)
J
/
10
-3
MHz
0.07320(12)
0.07502(10)
0.07284(15)
0.07270(13)
K
/
10
-3
MHz
0.896(28)
0.864(52)
0.860(58)
0.860(59)
J
range
1 – 16
1 – 12
1 – 12
1 – 12
K
a
range
0 – 6
0 – 3
0 – 3
0 – 3
rms
/kHz
8.23
1.14
1.41
1.39Slide14
Ar-TFO - Structure
3.788(1) Å3.7491(7) Å
3.454(2) Å
Kisiel’s
STRFIT used to fit A, B, C of 4 isotopologues to 3 structural parameters locating the
Ar
atom
TFO fixed at monomer values
rms
= 0.048 u
Å
2
and well-behaved correlations
EVAL used to calculate
chemically relevant parameters
Observed structure is the
anti
conformer in contrast to the
syn
conformer seen in
methyloxirane
!
Blanco, Maris,
Millemaggi
,
Caminati
,
J.Mol
.
Struct
.,
612,
309 (2002).Slide15
SummaryThe microwave spectra and molecular structures for two potential chiral tags are determined.Both 2-(trifluoromethyl)-oxirane and 2-vinyloxirane have uncomplicated, easily assigned spectra.Both are easily available in racemic and enantiopure forms.2-(
trifluoromethyl)-oxirane is easier to incorporate into free-jet expansion.Alternate functionalizations may prove useful in forming non-covalant interactions with different partners.Argon–2-(trifluoromethyl)-oxirane is observed as the anti conformer in contrast to the syn conformer found for propylene oxide (2-methyloxirane).