The crystal structure of carbamoyl fluoride, NH2COF

Article abstract of DOI:10.1007/s11224-016-0875-x

Although first synthesized in 1940, the X-ray crystal structure of carbamoyl fluoride, NH₂COF, has until now remained unknown. [1] NH₂COF crystallizes in the orthorhombic space group Ibam, is planar, and exhibits a short C-N bond length, 1.3168(13) ?, implying a significant degree of donation from the nitrogen lone pair. The structure features one molecule in the asymmetric unit and eight molecules in the unit cell. There are four molecules in two planar layers that are connected by a network of NH·O hydrogen bonds with N·O distances of 2.987(2) ? and 2.945(2) ?. The compound was also studied by quantum chemical calculations at both the ab initio (MP2) and density functional theory (B3LYP) level.

Full text of DOI:10.1007/s11224-016-0875-x

Struct Chem
DOI 10.1007/s11224-016-0875-x
ORIGINAL RESEARCH
The crystal structure of carbamoyl fluoride, NH2COF
Amanda F. Baxter1 & Karl O. Christe1 & Ralf Haiges1
Received: 1 October 2016 /Accepted: 7 November 2016
#
Springer Science+Business Media New York 2016
Abstract Although first synthesized in 1940, the X-ray crys-
tal structure of carbamoyl fluoride, NH2COF, has until now
remained unknown. [1] NH2COF crystallizes in the ortho-
rhombic space group Ibam, is planar, and exhibits a short C-
N bond length, 1.3168(13) Å, implying a significant degree of
donation from the nitrogen lone pair. The structure features
one molecule in the asymmetric unit and eight molecules in
the unit cell. There are four molecules in two planar layers that
are connected by a network of NH·O hydrogen bonds with N·
O distances of 2.987(2) Å and 2.945(2) Å. The compound was
also studied by quantum chemical calculations at both the ab
initio (MP2) and density functional theory (B3LYP) level.
the crystal structure of the compound remained unknown
for more than 75 years.
Later, Olah and coworkers shed light on the structure and
reactivity of carbamoyl fluoride and its N-methyl and N,N-
dimethyl derivatives in solution by 1H and 19F NMR spec-
troscopy. [2] In SO2 solution at −40 °C, the 19F spectrum of
NH2COF revealed a doublet of multiplets at 12.7 ppm, in-
dicating that the protons are not equivalent due to hindered
rotation around the N-C(F) bond. From the NMR data, they
deduced that the structure features a partial C-N double
bond with a partial positive charge on the nitrogen and
partial negative charge on the oxygen. The reaction of
NH2COF with SbF5 yields a neutral O-coordinated Lewis
acid adduct, rather than the salt, [NH2CO]+[SbF6]−. The O-
protonated species [NH2C(F)OH]+ is formed upon reaction
of carbamoyl fluoride with Bmagic acid^ HSO3F-SbF5 in
SO2 solution at low temperature. The NMR spectra of both
the SbF5 adduct and the protonated species also indicated
hindered rotation about the N-C(F) bond.
.
.
Keywords Carbamoyl fluoride NH2COF Carbamoyl
.
.
halide Crystal structure Hydrogen bonding
Introduction
The simplest carbamoyl fluoride, NH2COF, was first pre-
pared in 1940 by Linhard and Betz through the reaction of
isocyanic acid with anhydrous HF (Eq. 1). [1] Considering
this relatively straightforward synthesis and the stability of
NH2COF (MP = 46–47 °C), it is somewhat surprising that
Until now, complementary structural information in the
solid-state has remained unavailable. In fact, searching the
Cambridge Structural Database (CSD) [3] for the NC(O)F
substructure yields only two results, F2(O)S = NC(O)F and
SC = NC(O)F. [4, 5] To the best of our knowledge, we report
the first example of a crystal structure R2NCOF with an
amine-type rather than an imine-type N atom. It is also the
first example of a crystal structure of a primary carbamoyl
halide.
Electronic supplementary material The online version of this article
(doi:10.1007/s11224-016-0875-x) contains supplementary material,
which is available to authorized users.
* Ralf Haiges
haiges@usc.edu
1
Loker Hydrocarbon Research Institute and Department of Chemistry,
University of Southern California, Los Angeles, CA 90089-1661,
USA

Struct Chem
the slight lengthening of the C–N distance in NH2COF. The
observed bond angle pattern in NH2COF is different from the
ones in NH2COCF3, NH2COCF2CF2Cl, and NH2COCF2CF3.
While the N–C–O angle is significantly larger than 120° in all
three cases, and the sum of the bond angles around the carbon
atom is 360°, the two other angles (N-C-C and C-C-O) are sim-
ilar in the case of NH2COCF3, NH2COCF2CF2Cl, and
NH2COCF2CF3. In NH2COF, the N-C-O angle of 129.97(10)°
is significantly larger than in NH2COCF3 (126.8(3)°),
NH2COCF2CF2Cl (124.3(4)°), and NH2COCF2CF3
(125.3(2)°) with the bond angles around the central carbon atom
deviating substantially from 120° as predicted by the classical
VSEPR theory. [11–13] Based on a purely electronic argument,
one might expect that as the C–N bond gains double bond char-
acter, the N–C–O bond angle would increase as a result of elec-
tron–electron repulsion. With a highly electronegative group
X = F, CF3, CF2CF2Cl, orCF2CF3, it is also expected that O, X
repulsion will be a dominating factor. This argument is supported
by the fact that all X–C–O bond angles in Table 1 are within
117.1–118.5°. However, if the difference in bond angle pattern
would be purely due to electronic reasons, the bond distances of
NH2COF could be expected to be quite different from NH2COX.
Therefore, it seems that a steric argument can be made. The
fluorine atom is sterically much less demanding than CF3,
CF2CF2Cl, or CF2CF3 so that it is able to approach the nitrogen
atom yielding the small observed N–C–F angle of 111.56(8)°. It
is worth noting that SCNC(O)F and F2(O)SNC(O)F also exhibit
similarly small N–C–F bond angles of 109.6(2)°/110.7(2)° and
107.5(3)°, respectively (Table 2).
NH2COF crystallizes in the orthorhombic space group
Ibam with eight symmetry related molecules per unit cell
(Z = 8) that are aligned in two co-planar layers A and B
parallel to the 001 plane with an AB distance of 3.065(2) Å
(Fig. 2). The four molecules per unit cell within each layer are
associated through hydrogen bonds with the oxygen atom as
an acceptor to two N–H units of different molecules. One of
the N–H·O hydrogen bonds features an N·O distance of
2.987(2) Å and forms a centrosymmetric hydrogen-bonded
(NH2COF)2 dimer unit, typical for primary amides (Fig. 3).
[14] The same oxygen atom forms a second NH·O bond with
an N·O distance of 2.945(2) Å to a different molecule always
linking two (NH2COF)2 dimer units within the layers. One
might expect to observe NH·F hydrogen bonding in addition
to NH·O hydrogen bonds. The geometry is such that the N–H
Fig. 1. Asymmetric unit of NH2COF. Thermal ellipsoids are shown at
50% probability except for the hydrogen atoms which are depicted as
spheres of arbitrary radius. Bond lengths (Å) and angles (°): C1-O1
1.2099(12), C1-N1 1.3168(13), C1-F1 1.3510(11), N1-H1 0.869(17),
N1-H2 0.852(17), O1-C1-N1 129.97(10), O1-C1-F1 118.48(9), N1-C1-
F1 111.56(8), C1-N1-H1 119.7(10), C1-N1-H2 118.1(11), and H1-N1-
H2 122.2(14)
Results
Discussion
Amides are generally planar or nearly planar molecules as the
nitrogen atom donates its lone pair to the electrophilic carbon
atom. The extent to which this donation occurs is determined
by two factors: geometric constraints at the nitrogen atom and
the electronegativity of the substituent at carbon atom. [6, 7]
NH2COF can be viewed as an extreme in this respect with the
most electronegative element substituting the carbon atom and
a virtually unconstrained geometry at the nitrogen atom, ren-
dering the carbon atom extremely electrophilic.
It is therefore unsurprising that the molecule exhibits a planar
geometry with the sum of the bond angles at the central carbon
atom equal to 360.01(10)° (Fig. 1). The C–N bond distance of
1.3168(13) Å is significantly shorter than the average C–N bond
length of 1.327 Å for the primary amides in the CSD. The ob-
served C–N and C = O bond distances of NH2COF agree well
within the 3σ rule [10] with the ones of amides containing elec-
tronegative substituents (Table 1). It is noteworthy, however, that
the fluoroalkyl substituted analogs exhibit somewhat shorter C–
N distances. Although fluorine is highly electronegative and
therefore a σ-acceptor, it is also π-electron donating resulting in
Table 1 Selected bond distances
(Å) and angles (°) for NH2COX
X=
C–N
C = O
N–C–O
N–C–X
X–C–O
∑∠a
Lit.
F
1.3168(13)
1.311(4)
1.305(4)
1.302(2)
1.2099(12)
1.222(4)
1.231(3)
1.227(2)
129.97(10)
126.8(3)
124.3(4)
125.3(2)
111.56(8)
115.6(3)
117.8(3)
117.4(2)
118.48(9)
117.6(3)
117.8(3)
117.1(2)
360.01(9)
360.0(3)
359.9(3)
358.8(2)
This work
CF3
[8]
[9]
[9]
CF2CF2Cl
CF2CF3
a Sum of bond angles around the carbon atom

Struct Chem
Table 2 Bond angles (°) for the two other structurally characterized—
NC(O)F compounds in the CSD
N–C–O
N–C–F
F–C–O
SCNC(O)Fa
SCNC(O)Fa
F2(O)SNC(O)F
129.4(2)
128.2(2)
131.0(3)
109.6(2)
110.7(2)
107.5(3)
121.0(2)
121.0(2)
121.5(2)
a The crystal structure of SCNC(O)F contains two non-equivalent
molecules
vector is not nearly linear to the C–F vector (NH·F an-
gles = 109.13° and 95.08°), lessening the strength of this inter-
action. Although there are short N·F contacts of 2.891(2) Å, this
unfavorable orientation for hydrogen bonding leads to NH·F
distances of 3.551(2) Å and 3.350(2) Å IUPAC generally con-
siders a hydrogen bond to have an XH·Yangle greater than 110°.
[15] While it should be noted that both the N·F (2.891 Å) and N·
H (2.498 Å) distances are less than the sum of the van der Waals
radii (N + F = 3.02 Å, F + H = 2.67 Å), [16] these are probably
best described as weak electrostatic interactions. By contrast, the
N–H·O angles are 164.53° and 165.73°.
This interesting structure is stabilized by additional weak
electrostatic interactions (Fig. 4) resulting in short C·O and C·
C contacts of 3.075(3) Å and 3.343(3) Å, respectively, that are
shorter than the sum of van der Waals radii (C + C = 3.22 Å,
C + O = 3.40 Å) [16].
Fig. 3 The packing diagram for the NH2COF crystal structure normal to
the 001 plane displaying the centrosymmetric hydrogen-bonded dimers
whose centers correspond to the centers of symmetry of the unit cell
In order to gain further insight into the electronic structure
of NH2COF, we turned to theoretical calculations. The geom-
etry optimizations were carried out at the B3LYP6–311++
G(3df, 3pd) and B3LYP//aug-cc-pVQZ density functional
theory levels of theory as well as the correlated molecular
orbital theory MP2//6–311++G(3df, 3pd) level. The results
are summarized in Table 3. The calculated and experimental
bond distances are in reasonable agreement (percent differ-
ence = 0.2 to 2.3). The bond distances calculated at the
MP2/6–311++G(3df, 3pd) level correlate the best with the
experimental values. The largest disagreement, independent
of the method, is found for the C–N bond distance which is
consistently overestimated by 0.029–0.030 Å. The C = O
bond distance is consistently underestimated although the de-
viations are to a smaller degree than for the C–N distance
(0.019 Å for MP2/6–311++G(3df, 3pd)). The C–F bond
length calculated at the MP2 level of theory deviates by only
0.002 Å from the experimental value. Solid-state packing ef-
fects, such as the observed hydrogen bonding as well as the
electrostatic interlayer interactions between carbon and oxy-
gen atoms that would not be accounted for in the calculated
structure could contribute to the discrepancies between the
optimized structure and the crystal structure.
The calculated bond angles also correlate well with the crystal
structure (percent difference = 0.68 to 3.0). In this case, the larg-
est deviation, independent of the level of theory, was observed
Fig. 4 The packing diagram for the NH2COF crystal structure normal to
Fig. 2 The packing diagram for the NH2COF crystal structure normal to
the 010 plane depicting the BAB^ stacking of planar layers
the 100 plane depicting the electrostatic interactions between layers A and
B

Struct Chem
Table 3 Experimental and
calculated bond lengths (Å) and
angles (°) of NH2COF
C–N
C = O
C–F
N–C–O
N–C–F
F–C–O
Experimental
B3LYPa
B3LYPb
MP2a
1.3168(13)
1.3463
1.2099(10)
1.1877
1.3510(11)
1.3616
129.97(10)
129.05
111.56(8)
109.30
109.30
109.12
118.48(9)
121.66
1.3461
1.1876
1.3634
129.08
121.62
1.3471
1.1913
1.3537
128.87
122.02
a 6–311++G(3df, 3pd); b aug-cc-pVQZ
for the F–C–O bond angle which was consistently overestimated
by 3.14–3.54°. Contrary to what was observed with the bond
distances, the B3LYP method matched the bond angles of the
experimental crystal structure better than the MP2 method with
the B3LYP/aug-cc-pVQZ basis set giving slightly better values
than the B3LYP/6–311++G(3df, 3pd) basis set. Both the N–C–O
and N–C–F bond angles were calculated to be less than they
were observed in the crystal structure.
All in all, the calculated structure correlates quite well with
the experimental structure especially considering the degree of
stabilizing intermolecular interactions that are observed in the
crystal packing.
Theoretical calculations
Quantum chemical calculations were performed using
Gausian 09. [19] Ab initio (MP2) [20], and density functional
theory (B3LYP) [21–24] methods were implemented to opti-
mize the geometries using the 6–311++G(3df, 3pd) basis set.
B3LYP calculations were also performed with the aug-cc-
pVQZ basis set. Frequency calculations were also undertaken
to ensure that a true global minimum on the potential energy
surface was achieved.
Crystallographic details
The X-ray intensity data were measured on a Bruker APEX
DUO system equipped with a TRIUMPH curved-crystal mono-
chromator and a MoKα fine-focus tube (λ = 0.71073 Å). The
structures were solved by the direct method and refined on F2
using the Bruker SHELXTL Software Package and ShelXle.
[25–27] ORTEP drawings were prepared using the ORTEP-3
for Windows V2.02 program. [28] Further crystallographic de-
tails can be obtained from the Cambridge Crystallographic Data
Centre (CCDC, 12 Union Road, Cambridge CB21EZ, UK (Fax:
(+44) 1223–336–033; e-mail: deposit@ccdc.cam.ac.uk) on quot-
ing the deposition no. CCDC 1507419.
Experimental
Caution! Anhydrous HF can cause severe burns. Contact with
the skin must be avoided.
KOCN was dried by heating to 120 °C under dynamic
vacuum for at least 24 h prior to use. Stearic acid was dried
similarly but at room temperature. HF was dried by storage
over BiF5. Volatile materials were handled on a glass or stain-
less steel/Teflon-FEP vacuum line while solids were handled
under the dry nitrogen atmosphere of a glove box. [17]
Reactions with HF were carried out in Teflon/FEP ampules
closed with stainless steel valves.
HNCO was prepared by reacting stearic acid with KOCN at
130 °C. [18] As HNCO rapidly polymerizes near ambient tem-
perature, it was transferred to an FEP reactor immediately after it
was prepared, and frozen at −196 °C. A large excess of HF was
condensed onto it, and the reaction mixture was warmed up to
−78 °C where it was allowed to stand for 30 min. Then the
volatile compounds were removed slowly under dynamic vacu-
um first at −78 °C and gradually at ambient temperature.
Following removal of the volatile compounds, colorless
NH2COF crystals were obtained that were suitable for single
crystal X-ray diffraction. The material was confirmed to be pure
by NMR spectroscopy in SO2 solution at −30 °C (1H: δ = 6.07
(br); 14N: δ = −309.99 (s, Δν1/2 = 195 Hz); and 19F: δ = −11.03
(d)). 1H and 19F NMR spectra were recorded on a Varian NMRS-
500 spectrometer and were referenced externally to neat
Si(CH3)4 or 80% CFCl3 in CDCl3, respectively. 14N NMR spec-
tra were recorded on a Bruker AMX500 spectrometer and were
referenced to CH3NO2.
Conclusion
More than 75 years after its initial synthesis, we report the
crystal structure of NH2COF. This is the first crystal structure
of a primary carbamoyl halide and of any compound R2NCOF
with an amine-type nitrogen atom. The molecular structure of
the compound as determined by X-ray crystallography is in-
teresting as it contains bond angles around the central carbon
atom that deviate substantially from the 120° predicted by
VSEPR, much more so than amides NH2COX (where X is a
perhaloalkyl group) that are similar from an electronic point of
view. In the solid-state structure, the molecules are connected
by hydrogen bonds and are aligned in co-planar layers that are
parallel to the 001 plane of the crystal. Two distinct types of
N–H·O hydrogen bonds are observed: A slightly longer bond
of 2.987(2) Å arranging the molecules into (NH2COF)2 di-
mers and a slightly shorter one of 2.945(2) Å linking the dimer
units within the layers. The layers are linked by weak

Struct Chem
10. Pukelsheim F (1994) The three sigma rule. Am Stat 48(2):88–91.
doi:10.2307/2684253
interactions between the carbon and oxygen atoms of each
layer. Although N–H·F bonding is not formally observed,
these may be considered weak electrostatic interactions as
well. Despite this network of intermolecular interactions in
the solid-state structure, the optimized geometries obtained
at the B3LYP//6–311++G(3df, 3pd) and B3LYP//aug-cc-
pVQZ density functional theory levels of theory as well as
the correlated molecular orbital theory MP2//6–311++G(3df,
3pd) level methods match the experimental geometry reason-
ably well.
11. Gillespie RJ (1970) The electron-pair repulsion model for molecu-
lar geometry. J Chem Edu 47(1):18. doi:10.1021/ed047p18
12. Gillespie RJ (2008) Fifty years of the VSEPR model. Coord Chem
Rev 252(12–14):1315–1327. doi:10.1016/j.ccr.2007.07.007
13. Gillespie RJ, Nyholm RS (1957) Inorganic stereochemistry. Quarterly
Rev, Chem Soc 11(4):339–380. doi:10.1039/QR9571100339
14. Leiserowitz L, Schmidt GMJ (1969) Molecular packing modes.
Part III. Primary amides. J Chem Soc A (0):2372–2382.
doi:10.1039/J19690002372
15. Arunan E, Desiraju Gautam R, Klein Roger A, Sadlej J, Scheiner S,
Alkorta I, Clary David C, Crabtree Robert H, Dannenberg Joseph J,
Hobza P, Kjaergaard Henrik G, Legon Anthony C, Mennucci B,
Nesbitt David J (2011) Definition of the hydrogen bond (IUPAC
recommendations 2011). Pure Appl Chem:83. doi:10.1351/PAC-
REC-10-01-02
Acknowledgments The Office of Naval Research (ONR) and the
Defense Threat Reduction Agency (DTRA) funded this work. We also
thank the Hydrocarbon Research Foundation for financial support. A.F.B.
acknowledges the National Science Foundation for a Graduate Research
Fellowship. We also wish to thank Profs. G. A. Olah and G. K. S.
Prakash, Drs. E. Byrd, M. Rahm, M. Vasiliu, W. Wilson, R. Wagner,
and G. B. Chabot, as well as S. Krishnamoorthy, P. Deokar, and T. Saal
for their help and stimulating discussions.
16. Bondi A (1964) van der Waals Volumes and Radii. J Phys Chem
68(3):441–451. doi:10.1021/j100785a001
17. Christe KO, Wilson RD, Schack CJ, Desmarteau DD (2007) Chloryl
Fluoride. In: Inorg. Synth. John Wiley & Sons, Inc., pp 3–6
18. Fischer GG, Janna, Klapötke TM, Krumm B (2002) Synthesis,
properties and dimerization study of isocyanic acid. Z Naturforsch
B: J Chem Sci 57(1):19–24
References
19. Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA,
Cheeseman JR, Scalmani G, Barone V, Mennucci B, Petersson
GA, Nakatsuji H, Caricato M, Li X, Hratchian HP, Izmaylov AF,
Bloino J, Zheng G, Sonnenberg JL, Hada M, Ehara M, Toyota K,
Fukuda R, Hasegawa J, Ishida M, Nakajima T, Honda Y, Kitao O,
Nakai H, Vreven T, Montgomery Jr JA, Peralta JE, Ogliaro F,
Bearpark MJ, Heyd J, Brothers EN, Kudin KN, Staroverov VN,
Kobayashi R, Normand J, Raghavachari K, Rendell AP, Burant JC,
Iyengar SS, Tomasi J, Cossi M, Rega N, Millam NJ, Klene M,
Knox JE, Cross JB, Bakken V, Adamo C, Jaramillo J, Gomperts
R, Stratmann RE, Yazyev O, Austin AJ, Cammi R, Pomelli C,
Ochterski JW, Martin RL, Morokuma K, Zakrzewski VG, Voth
GA, Salvador P, Dannenberg JJ, Dapprich S, Daniels AD, Farkas
Ö, Foresman JB, Ortiz JV, Cioslowski J, Fox DJ (2009) Gaussian
09. Gaussian, Inc., Wallingford, CT, USA
1. Linhard M, Betz K (1940) Über Cyansäure IV: Die Konstitution der
Cyansäure. Carbaminsäurefluorid und -bromid. Chem Ber 73(3):
177–185. doi:10.1002/cber.19400730305
2. Olah GA, Nishimura J, Kreienbuehl P (1973) Stable carbocations.
CLXI. Protonation and Lewis acid halide complex formation of
carbamyl halides and alkyl (aryl) isocyanates and isothiocyanates.
Carbamyl, thiocarbamyl, and allophanyl cations. J Am Chem Soc
95(23):7672–7680. doi:10.1021/ja00804a022
3. Groom CR, Bruno IJ, Lightfoot MP, Ward SC (2016) The
Cambridge structural database. Acta Cryst B 72(2):171–179.
doi:10.1107/S2052520616003954
4. Boese R, Cutin EH, Mews R, Robles NL, Della Védova CO (2005)
((Fluoroformyl)imido)sulfuryl difluoride, FC(O)NS(O)F2: struc-
tural, conformational, and configurational properties in the gaseous
and condensed phases. Inorg Chem 44(26):9660–9666.
doi:10.1021/ic050808q
5. Ramos LA, Ulic SE, Romano RM, Erben MF, Lehmann CW,
Bernhardt E, Beckers H, Willner H, Della Védova CO (2010)
Vibrational spectra, crystal structures, constitutional and rotational
isomerism of FC(O)SCN and FC(O)NCS. Inorg Chem 49(23):
11142–11157. doi:10.1021/ic101741e
6. Kirby AJ, Komarov IV, Wothers PD, Feeder N (1998) The most
twisted amide: structure and reactions. Angew Chem Int Ed 37(6):
785–786. doi:10.1002/(SICI)1521-3773(19980403)37:6<785
::AID-ANIE785>3.0.CO;2-J
7. Quinonero D, Frontera A, Capo M, Ballester P, Suner GA, Garau C,
Deya PM (2001) The resonance model in amides: a combined
crystallographic and ab initio investigation. New J Chem 25(2):
259–261. doi:10.1039/B008260K
20. Møller C, Plesset MS (1934) Note on an approximation treatment
for many-electron systems. Phys Rev 46(7):618–622
21. Becke AD (1993) Density-functional thermochemistry. III. The role of
exact exchange. J Chem Phys 98(7):5648–5652. doi:10.1063/1.464913
22. Lee C, Yang W, Parr RG (1988) Development of the Colle-Salvetti
correlation-energy formula into a functional of the electron density.
Phys Rev B 37(2):785–789
23. Stephens PJ, Devlin FJ, Chabalowski CF, Frisch MJ (1994) Ab
initio calculation of vibrational absorption and circular dichroism
spectra using density functional force fields. J Phys Chem 98(45):
11623–11627. doi:10.1021/j100096a001
24. Vosko SH, Wilk L, Nusair M (1980) Accurate spin-dependent electron
liquid correlation energies for local spin density calculations: a critical
analysis. Can J Phys 58(8):1200–1211. doi:10.1139/p80-159
25. Sheldrick GM (2008) A short history of SHELX. Acta Cryst A 64:
112–122
26. Sheldrick GM (2012) SHELXL. vol 2012–1 ed., Vol. 2012–4 edn.
27. Sheldrick GM (2015) Crystal structure refinement with SHELXL.
Acta Cryst C 71:3–8
28. Farrugia LJ (1997) ORTEP-3 for windows—a version of ORTEP-
III with a graphical user Interface (GUI). J Appl Crystallogr 30(5–
1):565–565. doi:10.1107/S0021889897003117
8. Kalyanaraman B, Kispert LD, Atwood JL (1978) The disordered crys-
tal structure of bromodifluoroacetamide and trifluoroacetamide. Acta
Cryst B 34(4):1131–1136. doi:10.1107/S0567740878005075
9. Chekhlov AN (2006) Crystalline and molecular structures of two
halogenated propionamides CF2XCF2CONH2 (X = H, Cl). J
Struct Chem 47(4):777–781. doi:10.1007/s10947-006-0370-0