Urea can crystallise with other compounds. These can be called urea adducts or if a solvent is involved, a urea solvate, and the process is called urea extraction crystallization. Urea can also be a neutral ligand if it is coordinated to a central metal atom. Urea can form hydrogen bonds to other oxygen and nitrogen atoms in the substance it crystallises with. This stiffens the solid and raises the melting point.[1] T

List edit

name formula ratio

urea: solute

crystal system space group unit cell volume density comment reference
hydrogen peroxide; urea (1:1) HOOH•CH4N2O 1:1 orthorhombic Pnca a 6.732 b 4.8207 c 12.873 Z=4 decomposes slowly at room temperature [2]
urea; acetic acid (1:2) 2CH3COOH•CH4N2O 1:2 monoclinic P21/n a 7.6549 b 10.1351 c 11.5219 β 99.570° Z=4 881.47 1.358 unstable in air [3]
oxalic acid; urea (1:1) C2H2O4•CH4N2O 1:1 monoclinic C2/c a 13.0625 b 6.6437 c 6.8478 β 92.474° [4]
oxalic acid; urea (1:2) C2H2O4•2CH4N2O 2:1 monoclinic P2/c a 5.058 b 12.400 c 6.964 β 98.13° [5]
Urea - N,N-dimethylformamide (3:1) 3CH4N2O·C3H7NO 3:1 triclinic P1 a = 7.525 b = 9.866 c = 10.821 α = 65.61° β = 79.43° γ = 70.76° Z=2 689.7 1.219 colourless @150K [6]
N,N-dimethylacetamide; urea (1:1) C4H9NO·CH4N2O 1:1 monoclinic C2/c a = 7.2770 b = 17.5394 c = 7.3789 β = 119.450° Z=4 820.11 1.192 colourless @120K [7]
Urea malonic acid 1:1 monoclinic P2/c a 13.091 b 5.455 c 9.933 β 104.39° [8]
Maleic acid; urea (1:1) 1:1 monoclinic Cc a 5.144 b 9.999 c 14.80 β 95.1° [9]
Succinic acid bis urea 2:1 monoclinic P21/c a 5.637 b 8.243 c 12.262 β 96.75° Z=2 565.81 1.41 [10]
Maleic acid; urea (2:1) 2:1 monoclinic P21/n a 5.661 b 11.754 c 19.173 β 91.56° [9]
Fumaric acid; urea (1:2) 1:2 monoclinic P21/c a 5.540 b 8.227 c 12.426 β 97.22° [11]
D-Tartaric 1:1 orthorhombic P212121 a 17.229 b 9.824 c 5.056 Z=4 1.63 transparent 255 to 1370 nm; SHG 3×KDP [12]
DL-Tartaric 1:1 monoclinic P21 a 7.6973 b 23.3310 c 4.8727 β 100.82° NLO; transparent from 240 to 1950 nm [13]
Gluatric acid bis urea 2:1 monoclinic C2/c a 11.954 b 10.932 c 9.078 β 97.86° Z=4 [14]
Itaconic acid 1:1 monoclinic P21/c a 12.71 b 5.2695 c 13.833β 104.78° [15]
2-bromotetradecane urea hexagonal P6122 a=8.2582 c=10.9937 298K [16]
2-bromotetradecane urea orthorhombic C2221 207K [16]
2-bromotetradecane urea monoclinic P21 a 16.338(1)Å b 10.9665(8)Å c 16.338(1)Å, α 90° β 60.00° [16]
4-amino benzoic acid; urea (2:1) (C7H7NO2)2(CH4N2O) 1:2 orthorhombic Pnab a=7.4159 b=11.870 c=18.750 [17]
salicylic acid; urea (1:1) 1:1 monoclinic C2/c a=22.206 b=5.108 c=17.177 β=106.18 Z=8° 1.407 [18]
5-nitro salicylic acid; urea (2:1) (C7H5NO5)2(CH4N2O) 1:2 triclinic P1 a=6.9889 b=12.1968 c=12.3622 α=60.923° β=81.169° γ=76.938° [17]
3,5-dinitro salicylic acid; urea (1:1) (C7H4N2O7)(CH4N2O) 1:1 monoclinic P21/c a=4.942 b=22.337 c=10.389 β=100.92° [17]
o-phthalic acid; urea (1:1) 1:1 triclinic P1 a=7.422 b=7.662 c=10.088 α=85.95° β=82.01° γ=65.14° [17]
urea : 1,4-dioxane (1 : 1) C4H8O2•C3H6O 1:1 monoclinic P2/c a=6.7949 b=4.5234 c=12.2711 β=95.701° Z=2 [1]
urea : morpholine (1 : 1) C4H8ON•C3H6O 1:1 orthorhombic Pbcm a=4.5847 b=19.131 c=8.9047 Z=4 [1]
3,5-dimethylpyridine bis(urea) (CH3)2C5H3N•2C3H6O 2:1 orthorhombic Abm2 a=21.737 b=7.2102 c=15.590 Z=8 2443.4 1.236 at 173K [19]
3,5-dimethylpyridine bis(urea) (CH3)2C5H3N•2C3H6O 2:1 monoclinic Cc a=8.5829 b=21.4843 c=7.2050 β=114.405° Z=4 1209.87 1.248 at 100K [19]
2,6-dimethylpyridine urea (CH3)2C5H3N•C3H6O 1:1 triclinic P1 a=7.4126 b=7.6720 c=8.1731 α=88.391° β=83.564° γ=80.059° Z=2 454.92 1.221 at 100K [19]
urea 2,6-dimethylpyridine (CH3)2C5H3N•C3H6O 1:1 monoclinic C2/c a=1.426 b=11.1168 c=7.4318 β=101.23° Z=4 925.9 1.200 at 200K [19]
2,6-dimethylpyridine bis(urea) (CH3)2C5H3N•2C3H6O 2:1 orthorhombic Pnma a=8.0772 b=7.2986 c=20.4169 Z=4 1203.64 1.254 at 100K [19]
2,6-dimethylpyridine bis(urea) (CH3)2C5H3N•2C3H6O 2:1 monoclinic C2/c a=11.160 b=11.5421 c=10.910 β=116.12° [17]
2-picoline; urea (1:1) C6H7N·CH4N2O 1:1 orthorhombic Pbca a = 7.471 b = 14.916 c = 15.338 Z = 8 1709.2 [20]
Urea pyrazine-2,3-dicarboxylic acid 1:1 monoclinic P21/n a=7.725 b=10.2530 c=12.612 β=97.997° [17]
bipyridine urea triclinic P1 a=7.200 b=8.297 c=9.835 α=75.849° β=70.744° γ =73.045° [21]
bipyridine urea triclinic P1 a=7.2862 b=8.3747 c=9.8647 α=76.061° β=72.789° γ=74.121° [21]
1,10-Phenanthroline urea 1:1 monoclinic C2/c a=14.342 b=12.002 c=7.3724 β 116.743° [21]
2,9-Dimethyl-1,10-phenanthroline urea 1:1 orthorhombic Cmcm a=11.370 b=17.351 c=7.3593 [21]
sodium chloride; urea; water (1:1:1) NaCl·CH4N2O·H2O 1:1 triclinic a = 6.44 Å, b = 5.245Å, c = 17.312 Å, and a=90°, β=90.15°, γ=90° 588.76 SHG 1.53 × KDP, birefringence 0.084@1064 nm UV edge 209 nm [22][23]
Bis(2-3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)bis[(3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)copper(II)]-urea-acetone (1/6/2) [Cu2(C10H11O2)4]·6CH4N2O·2C3H6O 5:1 monoclinic P21/c a 17.0125 b 11.0470 c 17.2731 β 110.385° Z=2 3042.95 1.371 green [24]
aqua(N-salicylidene-rac-alaninato- O,N,O')copper(II)-urea (1/1) 1:1 triclinic P1 a = 7.637, b = 8.509 c = 10.716 α = 93.10° β = 97.97° γ= 106.37° Z= 2, 658.5 blue [25]
Aqua[9-(1,8-diazafluoren-9-ylidene)amino-1,8-diazafluorenato]hydroxo(urea)zinc(II) urea solvate [Zn(C22H12N5)(OH)(CH4N2O)(H2O)]•C4N2O 1:1 monoclinic P21/c a 7.8637 b 16.0133 c 17.9513 β 101.358° Z=4 2216.2 1.687 purple [26]
Pentakis(carbamide)dioxoneptunium(V) nitrate [NpO2{OC(NH2)2}5](NO3) monoclinic P21 a = 11.142, b = 7.6379 c = 11.143 β = 108.9° Z = 2 897.1 [27]
Bis[(isothiocyanato)tetraureadioxoneptunium(V)] urea {NpO2(NCS)[OC(NH2)2]4}2 · OC(NH2)2 tetragonal P43212 a=7.851 c=56.84 Z=4 3504 2.265 light green [28]
1 αβγ

References edit

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