Hydrogen-deuterium substitution in solid ethanol by surface reactions at low temperatures

12 Pages·2017·0.75 MB·English

Title Hydrogen-deuterium substitution in solid ethanol by surface reactions at low temperatures
Author(s) Oba, Yasuhiro; Osaka, Kazuya; Chigai, Takeshi; Kouchi, Akira; Watanabe, Naoki
Monthly notices of the royal astronomical society, 462(1), 689-695
Citation
https://doi.org/10.1093/mnras/stw1714
Issue Date 2016-07-18
Doc URL http://hdl.handle.net/2115/63550
This article has been accepted for publication in　Monthly notices of the royal astronomical society, © 2016,Oba,
Rights Yasuhiro; Osaka, Kazuya; Chigai, Takeshi; Kouchi, Akira; Watanabe, Naoki, Published by Oxford University Press on
behalf of The Royal Astronomical Society. All rights reserved.
Type article
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Supporting Information

Hydrogen–deuterium substitution in solid ethanol by surface reactions
at low temperatures

Yasuhiro Oba,1 Kazuya Osaka,1 Takeshi Chigai,1 Akira Kouchi,1 Naoki Watanabe1
1Institute of Low Temperature Science, Hokkaido University,
N19W8, Kita-ku, Sapporo, Hokkaido 060-0189 Japan

Contents
1. Possible H-D and D-H substitution reactions of ethanol isotopologues
2. Other chemical reactions
3. Rate equations for all ethanol isotopologues
4. Additional Figures A1-A5
1. Possible H-D and D-H substitution reactions of ethanol isotopologues.
We consider that H–D substitution of CD CH OH and CH CD OH proceeds
3 2 3 2
through the successive H abstraction-D addition reactions as follows:
CD CH OH + D → CD CHOH + HD, (A1a)
3 2 3
CD CHOH + D → CD CHDOH, (A1b)
3 3
CD CHDOH + D → CD CDOH + HD, (A2a)
3 3
CD CDOH + D → CD CD OH. (A2b)
3 3 2
CH CD OH + D → CH CD OH + HD, (A3a)
3 2 2 2
CH CD OH + D → CH DCD OH, (A3b)
2 2 2 2
CH DCD OH + D → CHDCD OH + HD, (A4a)
2 2 2
CHDCD OH + D → CHD CD OH, (A4b)
2 2 2
CHD CD OH + D → CD CD OH + HD, (A5a)
2 2 2 2
CD CD OH + D → CD CD OH. (A5b)
2 2 3 2
The hydroxyl group of ethanol did not exchange its hydrogen with D atoms.
For the D–H substitution, the following reactions are considered to occur at
low temperatures:
CH CD OH + H → CH CDOH + HD, (A6a)
3 2 3
CH CDOH + H → CH CHDOH. (A6b)
3 3
CH CHDOH + H → CH CHOH + HD, (A7a)
3 3
CH CHOH + H → CH CH OH. (A7b)
3 3 2
CD CH OH + H → CD CH OH + HD, (A8a)
3 2 2 2
CD CH OH + H → CHD CH OH. (A8b)
2 2 2 2
CHD CH OH + H → CHDCH OH + HD, (A9a)
2 2 2
CHDCH OH + H → CH DCH OH, (A9b)
2 2 2
CH DCH OH + H → CH CH OH + HD. (A10a)
2 2 2 2
CH CH OH + H → CH CH OH. (A10b)
2 2 3 2

2. Other chemical reactions
We found that a small peak was observed at ~1715 cm-1 when ethanol
isotopologues were exposed to H or D atoms (e.g. Figures 2 & 3). Since ethanol
isotopologues do not have absorption at this region (Figure 1), this peak could be
derived from other species except for ethanol. One of the possible scenarios is that this
peak is derived from the C=O stretching band of acetaldehyde (CH CHO) or its
3
deuterated isotopologues. In the reaction of CH CH OH with D, for example, the
3 2
formation of acetaldehyde might be possible through the following successive hydrogen
abstraction reactions:
CH CH OH + D → CH CHOH + HD, (1a)
3 2 3
CH CHOH + D → CH CHO + HD. (A11)
3 3
Xu et al. (2012) showed that reaction (A11) is exothermic with an activation barrier in
the gas phase (~13 kJ mol-1). Although the main product of the reaction of CH CHOH
3
with D should be CH CHDOH (reaction 1b), reaction (A11) could also proceed even at
3
10 K via quantum tunnelling.
Another candidate for the 1715 cm-1 band is the C=C stretching band of vinyl
alcohol, CH =CHOH, which could be formed from CH CHOH by the following
2 3
exothermic hydrogen abstraction reaction:
CH CHOH + D → CH =CHOH + HD. (A12)
3 2
Since the activation barrier of reaction (A12) is lower than reaction (A11) by ~10 kJ
mol-1 (Xu et al. 2012), reaction (A12) may preferentially occur over reaction (A11).
Nevertheless, both reactions (A11) and (A12) should be very minor compared to the
competitive barrierless reaction (1b), which results in the conclusion that the
contribution to the obtained kinetic parameter should be very small. This is consistent
with the weak intensity of the observed 1715 cm-1 band for the possible reaction
products.
3. Rate equations for all ethanol isotopologues.
N represents the number density of species X (H, D, or ethanol
X
isotopologues).
dN /dt = –k N N + k N N – k N N +
CH3CH2OH CH3-D D CH3CH2OH CD3-H H CH2DCH2OH CH2-D D CH3CH2OH
k N N , (12)
CD2-H H CH3CHDOH
dN /dt = k N N – k N N – k N N +
CH2DCH2OH CH3-D D CH3CH2OH CD3-H H CH2DCH2OH CH3-D D CH2DCH2OH
k N N – k N N + k N N ,
CD3-H H CHD2CH2OH CH2-D D CH2DCH2OH CD2-H H CH2DCHDOH
(A12)
dN /dt = k N N – k N N – k N N +
CH3CHDOH CH2-D D CH3CH2OH CD2-H H CH3CHDOH CH3-D D CH3CHDOH
k N N – k N N + k N N ,
CD3-H H CH2DCHDOH CH2-D D CH3CHDOH CD2-H H CH3CD2OH
(A13)
dN /dt = k N N – k N N – k N N +
CHD2CH2OH CH3-D D CH2DCH2OH CD3-H H CHD2CH2OH CH3-D D CHD2CH2OH
k N N – k N N + k N N ,
CD3-H H CD3CH2OH CH2-D D CHD2CH2OH CD2-H H CHD2CHDOH
(A14)
dN /dt = k N N – k N N + k N N –
CH2DCHDOH CH2-D D CH2DCH2OH CD2-H H CH2DCHDOH CH3-D D CH3CHDOH
k N N – k N N + k N N –
CD3-H H CH2DCHDOH CH3-D D CH2DCHDOH CD3-H H CHD2CHDOH
k N N + k N N , (A15)
CH2-D D CH2DCHDOH CD2-H H CH2DCD2OH
dN /dt = k N N – k N N – k N N +
CH3CD2OH CH2-D D CH3CHDOH CD2-H H CH3CD2OH CH3-D D CH3CD2OH
k N N , (A16)
CD3-H H CH2DCD2OH
dN /dt = k N N – k N N – k N N +
CD3CH2OH CH3-D D CHD2CH2OH CD3-H H CD3CH2OH CH2-D D CD3CH2OH
k N N , (A17)
CD2-H H CD3CHDOH
dN /dt = k N N – k N N + k N N –
CHD2CHDOH CH2-D D CHD2CH2OH CD2-H H CHD2CHDOH CH3-D D CH2DCHDOH
k N N – k N N + k N N –
CD3-H H CHD2CHDOH CH3-D D CHD2CHDOH CD3-H H CD3CHDOH
k N N + k N N , (A18)
CH2-D D CHD2CHDOH CD2-H H CHD2CD2OH
dN /dt = k N N – k N N + k N N –
CH2DCD2OH CH2-D D CH2DCHDOH CD2-H H CH2DCD2OH CH3-D D CH3CD2OH
k N N – k N N + k N N ,
CD3-H H CH2DCD2OH CH3-D D CH2DCD2OH CD3-H H CHD2CD2OH
(A19)
dN /dt = k N N – k N N + k N N –
CD3CHDOH CH2-D D CD3CH2OH CD2-H H CD3CHDOH CH3-D D CHD2CHDOH
k N N – k N N + k N N ,
CD3-H H CD3CHDOH CH2-D D CD3CHDOH CD2-H H CD3CD2OH
(A20)
dN /dt = k N N – k N N + k N N –
CHD2CD2OH CH2-D D CHD2CHDOH CD2-H H CHD2CD2OH CH3-D D CH2DCD2OH
k N N – k N N + k N N ,
CD3-H H CHD2CD2OH CH3-D D CHD2CD2OH CD3-H H CD3CD2OH
(A21)
dN /dt = k N N – k N N + k N N –
CD3CD2OH CH2-D D CD3CHDOH CD2-H H CD3CD2OH CH3-D D CHD2CD2OH
k N N , (A22)
CD3-H H CD3CD2OH
4. Additional Figures

FIG. A1
(a) Infrared spectrum of solid CD CH OH, (b) difference spectra of CD CH OH after
3 2 3 2
exposure to D atoms for up to 180 min, and (c) infrared spectrum of solid CD CD OH.
3 2
FIG. A2
(a) Infrared spectrum of solid CH CD OH, (b) difference spectra of CH CD OH after
3 2 3 2
exposure to D atoms for up to 180 min, and (c) infrared spectrum of solid CD CD OH.
3 2
FIG. A3
(a) Infrared spectrum of solid CH CD OH, (b) difference spectra of CH CD OH after
3 2 3 2
exposure to H atoms for up to 60 min, and (c) infrared spectrum of solid CH CH OH.
3 2