Structure determination of lithium chloroacetate, lithium bromoacetate and lithium iodoacetate by powder diffraction

Most halogenoacetates of alkali salts readily undergo a thermally induced polymerization reaction to poly-(hydroxyacetic acid) in the solid state. The lithium salts represent a remarkable exception. The crystal structures of lithium chloroacetate, lithium bromoacetate and lithium iodoacetate were determined ab initio from synchrotron powder diffraction data. The three compounds are isostructural and differ considerably from the structures of sodium chloroacetate and silver chloroacetate, two compounds that undergo polymerization. Most likely, the strong polarizing effect of the small lithium cation is responsible for the unfavorable crystal structure in which each lithium cation is coordinated to four O atoms from four different halogenoacetate molecules. Lithium chloroacetate: a = 9.3882 (9), b = 4.8452 (4), c = 9.0119 (7) Å, β = 94.330 (5)°; lithium bromoacetate: a = 9.7165 (11), b = 4.8610 (6), c = 9.0228 (11) Å, β = 93.946 (5)°; lithium iodoacetate: a = 10.1812 (10), b = 4.8922 (8), c = 9.0468 (10) Å, β = 93.251 (5)°, all crystallizing in space group P2₁/c with Z = 4.

Computing details

For all compounds, cell refinement: FULLPROF; program(s) used to refine structure: FULLPROF.

Figures

(cl) chloroacetic acid, lithium salt

Crystal data

C2H2ClLiO2	Z = 4
Mr = 100.43	Melting point: 483.7 K
Monoclinic, P21/c	Synchrotron radiation, λ = 1.2841 Å
a = 9.3882 (9) Å	T = 298 K
b = 4.8452 (4) Å	Particle morphology: platelets
c = 9.0119 (7) Å	colorless
β = 94.330 (5)°	cylinder, ? × ? × ? mm
V = 408.76 (6) Å^3

Data collection

HASYLAB (Hamburg, Germany), Beamline B2 diffractometer	Scan method: step
Germanium monochromator	2θmin = 6°, 2θmax = 60°, 2θstep = 0.01°

Refinement

Rp = 3.25	Profile function: Pseudo-Voigt
Rwp = 4.21
Rexp = 1.88	Background function: Fixed background
χ^2 = 5.018	Preferred orientation correction: March's function
5938 data points

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cl(1)	0.3600 (7)	0.139 (1)	0.1519 (7)	0.108
O(1)	0.112 (1)	0.316 (2)	0.962 (1)	0.005
O(2)	0.098 (2)	−0.051 (3)	0.826 (1)	0.005
C(1)	0.148 (2)	0.089 (3)	0.933 (2)	0.005
C(2)	0.279 (2)	−0.093 (3)	0.008 (2)	0.005
Li(1)	−0.007 (4)	0.583 (7)	0.856 (4)	0.005

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl(1)	0.026 (1)	0.097 (2)	0.021 (1)	0.022 (1)	−0.008 (1)	−0.014 (1)

Geometric parameters (Å, º)

Cl(1)—C(2)	1.84	Li(1)—O(1)	1.91
C(1)—C(2)^i	1.62	Li(1)—O(1)^ii	2.03
C(1)—O(1)	1.19	Li(1)—O(2)^iii	1.91
C(1)—O(2)	1.24	Li(1)—O(2)^iv	2.06
C(1)^i—C(2)^i—C(1)	102.7	O(1)—Li(1)—O(1)^ii	93.5
O(1)—C(1)—O(2)	125.5	O(2)^iii—Li(1)—O(2)^iv	111.7
C(2)^i—C(1)—O(1)	129.6	O(1)—Li(1)—O(2)^iii	113.9
C(2)^i—C(1)—O(2)	104.7	O(1)—Li(1)—O(2)^iv	112.3

Symmetry codes: (i) x, y, z+1; (ii) −x, −y+1, −z+2; (iii) −x, y+1/2, −z+3/2; (iv) x, y+1, z.

(br) bromoacetic acid, lithium salt

Crystal data

C2H2BrLiO2	Z = 4
Mr = 144.88	Melting point: 478.5 K
Monoclinic, P21/c	Synchrotron radiation, λ = 1.2841 Å
a = 9.7165 (11) Å	T = 298 K
b = 4.8610 (6) Å	Particle morphology: platelets
c = 9.0228 (11) Å	colorless
β = 93.946 (5)°	cylinder, ? × ? × ? mm
V = 425.15 (9) Å^3

Data collection

HASYLAB (Hamburg, Germany), Beamline B2 diffractometer	Scan method: step
Germanium monochromator	2θmin = 6°, 2θmax = 61°, 2θstep = 0.01°

Refinement

Rp = 4.76	Profile function: Pseudo-Voigt
Rwp = 6.18
Rexp = 2.76	Background function: Fixed background
χ^2 = 5.018	Preferred orientation correction: March's function
6701 data points

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Br(1)	0.3679 (3)	0.1644 (7)	0.1544 (5)	0.058
O(1)	0.102 (1)	0.305 (4)	0.969 (2)	0.004
O(2)	0.089 (2)	−0.067 (3)	0.824 (2)	0.004
C(1)	0.140 (3)	0.070 (5)	0.921 (3)	0.004
C(2)	0.269 (2)	−0.083 (5)	0.010 (3)	0.004
Li(1)	0.000 (5)	0.60 (1)	0.858 (6)	0.004

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br(1)	0.009 (1)	0.051 (1)	0.016 (1)	0.009 (1)	−0.009 (1)	−0.009 (1)

Geometric parameters (Å, º)

Br(1)—C(2)	1.97	Li(1)—O(1)	1.99
C(1)—C(2)^i	1.62	Li(1)—O(1)^ii	1.97
C(1)—O(1)	1.29	Li(1)—O(2)^iii	1.99
C(1)—O(2)	1.18	Li(1)—O(2)^iv	1.85
Br(1)^i—C(2)^i—C(1)	111.9	O(1)—Li(1)—O(1)^ii	91.4
O(1)—C(1)—O(2)	129.7	O(2)^iii—Li(1)—O(2)^iv	114.1
C(2)^i—C(1)—O(1)	117.8	O(1)—Li(1)—O(2)^iii	119.6
C(2)^i—C(1)—O(2)	112.3	O(1)—Li(1)—O(2)^iv	106.5

Symmetry codes: (i) x, y, z+1; (ii) −x, −y+1, −z+2; (iii) −x, y+1/2, −z+3/2; (iv) x, y+1, z.

(i) iodoacetic acid, lithium salt

Crystal data

C2H2ILiO(2)	Z = 4
Mr = 191.88	Melting point: 530.2 K
Monoclinic, P21/c	Synchrotron radiation, λ = 1.2006 Å
a = 10.1812 (10) Å	T = 298 K
b = 4.8922 (8) Å	Particle morphology: platelets
c = 9.0468 (10) Å	colorless
β = 93.251 (5)°	cylinder, ? × ? × ? mm
V = 449.89 (10) Å^3

Data collection

HASYLAB (Hamburg, Germany), Beamline B2 diffractometer	Scan method: step
Germanium monochromator	2θmin = 6°, 2θmax = 50°, 2θstep = 0.01°

Refinement

Rp = 5.64	Profile function: Pseudo-Voigt
Rwp = 7.40
Rexp = 3.65	Background function: Fixed background
χ^2 = 4.121	Preferred orientation correction: March's function
4401 data points

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
I(1)	0.3739 (4)	0.181 (2)	0.1504 (8)	0.120
O(1)	0.106 (5)	0.32 (1)	0.953 (7)	0.038
O(2)	0.078 (3)	−0.07 (1)	0.831 (6)	0.038
C(1)	0.127 (8)	0.07 (2)	0.94 (1)	0.038
C(2)	0.249 (5)	−0.09 (1)	0.039 (9)	0.038
Li(1)	0.01 (1)	0.51 (4)	0.81 (2)	0.038

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I(1)	0.006 (1)	0.28 (1)	−0.004 (1)	0.012 (4)	−0.009 (1)	−0.013 (6)

Geometric parameters (Å, º)

I(1)—C(2)	2.07	Li(1)—O(1)	1.78
C(1)—C(2)^i	1.68	Li(1)—O(1)^ii	2.63
C(1)—O(1)	1.21	Li(1)—O(2)^iii	1.63
C(1)—O(2)	1.33	Li(1)—O(2)^iv	2.14
I(1)^i—C(2)^i—C(1)	110.2	O(1)—Li(1)—O(1)^ii	82.0
O(1)—C(1)—O(2)	121.7	O(2)^iii—Li(1)—O(2)^iv	116.9
C(2)^i—C(1)—O(1)	125.0	O(1)—Li(1)—O(2)^iii	133.9
C(2)^i—C(1)—O(2)	111.1	O(1)—Li(1)—O(2)^iv	107.8

Symmetry codes: (i) x, y, z+1; (ii) −x, −y+1, −z+2; (iii) −x, y+1/2, −z+3/2; (iv) x, y+1, z.