organic compounds
N-(7-Methyl-1,8-naphthyridin-2-yl)acetamide–acetic acid (1/1)
aCollege of Chemistry and Chemical Engineering, Yunnan Normal University, Kunming 650500, People's Republic of China, bSchool of Computer Science and Technology, Harbin Institute of Technology, Harbin 150001, People's Republic of China, and cSchool of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
*Correspondence e-mail: chishaoming@gmail.com
In the title adduct, C11H11N3O·C2H4O2, all non-H atoms of the acetamide molecule are roughly coplanar, with an r.m.s. deviation of 0.0720 Å. The dihedral angle between the ring plane and the acetamide group is 8.5 (2)°. In the crystal, O—H⋯N and N—H⋯O hydrogen bonds link the acetamide and acetic acid molecules.
Related literature
For the synthesis of 7-amino-2-methyl-1,8-naphthyridine, see: Brown (1965); Henry & Hammond (1977). For the coordination modes of 1,8-naphthyridine ligands, see: Zong et al. (2004); Zúñiga et al. (2011); Li et al. (2011); Gan et al. (2011). For their biological activity, see: Sivakumar et al. (2011); Roma et al. (2000); Badawneh et al. (2001); Nagasawa et al. (2011); Capozzi et al. (2012).
Experimental
Crystal data
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Refinement
|
Data collection: PROCESS-AUTO (Rigaku, 1998); cell PROCESS-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97.
Supporting information
10.1107/S1600536813005242/qm2092sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536813005242/qm2092Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536813005242/qm2092Isup3.cml
7-amino-2-methyl-1,8-naphthyridine(Brown, 1965; Henry & Hammond, 1977)(4.00 g, 0.025 mol) was added to an acetic anhydride (15 ml) solution in an atmosphere of nitrogen. The mixture was stirred at room temperature for 1 h. Followed by slow cooling to room temperature which gave flaky straw-colored crystals. Yield: 3.97 g (78%). In the
complex, the acetic acid component is formed from the reagent (acetic anhydride) used.H atoms were placed in calculated positions. The H atoms were constrained to an ideal geometry (C—H =0.96 Å, N—H =0.86 Å and O—H = 0.85 Å) and refined as riding atoms with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C), Uiso(H) = 1.2Ueq(N) and Uiso(H) = 1.5Ueq(O).
Data collection: PROCESS-AUTO (Rigaku, 1998); cell
PROCESS-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku/MSC, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).C11H11N3O·C2H4O2 | Z = 2 |
Mr = 261.28 | F(000) = 276 |
Triclinic, P1 | Dx = 1.315 Mg m−3 |
a = 8.3628 (17) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 9.0904 (18) Å | Cell parameters from 25 reflections |
c = 9.5093 (19) Å | θ = 3.1–26.0° |
α = 71.30 (3)° | µ = 0.10 mm−1 |
β = 76.43 (3)° | T = 293 K |
γ = 78.64 (3)° | Flaky, yellow |
V = 659.8 (2) Å3 | 0.15 × 0.10 × 0.07 mm |
Rigaku R-AXIS RAPID diffractometer | 2591 independent reflections |
Radiation source: fine-focus sealed tube | 1014 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.058 |
ω scans | θmax = 26.0°, θmin = 3.1° |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | h = −10→10 |
Tmin = 0.986, Tmax = 0.993 | k = −11→10 |
5757 measured reflections | l = −11→11 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.047 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.160 | H-atom parameters constrained |
S = 0.91 | w = 1/[σ2(Fo2) + (0.0724P)2] where P = (Fo2 + 2Fc2)/3 |
2591 reflections | (Δ/σ)max < 0.001 |
172 parameters | Δρmax = 0.21 e Å−3 |
0 restraints | Δρmin = −0.20 e Å−3 |
C11H11N3O·C2H4O2 | γ = 78.64 (3)° |
Mr = 261.28 | V = 659.8 (2) Å3 |
Triclinic, P1 | Z = 2 |
a = 8.3628 (17) Å | Mo Kα radiation |
b = 9.0904 (18) Å | µ = 0.10 mm−1 |
c = 9.5093 (19) Å | T = 293 K |
α = 71.30 (3)° | 0.15 × 0.10 × 0.07 mm |
β = 76.43 (3)° |
Rigaku R-AXIS RAPID diffractometer | 2591 independent reflections |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | 1014 reflections with I > 2σ(I) |
Tmin = 0.986, Tmax = 0.993 | Rint = 0.058 |
5757 measured reflections |
R[F2 > 2σ(F2)] = 0.047 | 0 restraints |
wR(F2) = 0.160 | H-atom parameters constrained |
S = 0.91 | Δρmax = 0.21 e Å−3 |
2591 reflections | Δρmin = −0.20 e Å−3 |
172 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
N2 | 0.0316 (3) | 0.2121 (2) | 0.5279 (2) | 0.0452 (6) | |
N3 | 0.2361 (3) | 0.1068 (3) | 0.3663 (3) | 0.0504 (7) | |
O3 | 0.9707 (3) | −0.5868 (2) | 0.2515 (2) | 0.0681 (7) | |
H3A | 0.9822 | −0.6417 | 0.3366 | 0.102* | |
C6 | 0.1937 (4) | −0.0352 (3) | 0.6338 (3) | 0.0449 (8) | |
C10 | 0.1549 (4) | 0.0928 (3) | 0.5099 (3) | 0.0462 (8) | |
C3 | −0.0509 (4) | 0.2067 (3) | 0.6651 (3) | 0.0476 (8) | |
C4 | −0.0218 (4) | 0.0819 (3) | 0.7965 (3) | 0.0551 (9) | |
H4A | −0.0838 | 0.0818 | 0.8915 | 0.066* | |
O2 | 0.7624 (3) | −0.4612 (2) | 0.3776 (3) | 0.0735 (8) | |
C5 | 0.1006 (4) | −0.0375 (3) | 0.7772 (3) | 0.0541 (9) | |
H5A | 0.1223 | −0.1213 | 0.8603 | 0.065* | |
N1 | −0.1743 (3) | 0.3336 (3) | 0.6728 (3) | 0.0537 (8) | |
H1A | −0.1948 | 0.3949 | 0.5872 | 0.064* | |
O1 | −0.2586 (3) | 0.2989 (3) | 0.9261 (2) | 0.0799 (8) | |
C7 | 0.3229 (4) | −0.1511 (3) | 0.6026 (4) | 0.0559 (9) | |
H7A | 0.3533 | −0.2369 | 0.6808 | 0.067* | |
C12 | 0.8447 (4) | −0.4767 (3) | 0.2609 (4) | 0.0577 (9) | |
C8 | 0.4028 (4) | −0.1383 (3) | 0.4598 (4) | 0.0564 (9) | |
H8A | 0.4878 | −0.2153 | 0.4384 | 0.068* | |
C1 | −0.3839 (4) | 0.5235 (3) | 0.7581 (3) | 0.0659 (10) | |
H1B | −0.4453 | 0.5463 | 0.8492 | 0.099* | |
H1C | −0.4594 | 0.5117 | 0.7016 | 0.099* | |
H1D | −0.3215 | 0.6079 | 0.6984 | 0.099* | |
C9 | 0.3559 (4) | −0.0064 (3) | 0.3426 (3) | 0.0504 (8) | |
C11 | 0.4429 (5) | 0.0117 (4) | 0.1835 (4) | 0.0734 (11) | |
H11A | 0.3959 | 0.1073 | 0.1191 | 0.110* | |
H11B | 0.4302 | −0.0754 | 0.1526 | 0.110* | |
H11C | 0.5587 | 0.0150 | 0.1761 | 0.110* | |
C2 | −0.2675 (4) | 0.3748 (3) | 0.7971 (4) | 0.0549 (9) | |
C13 | 0.8161 (5) | −0.3725 (4) | 0.1088 (4) | 0.0802 (12) | |
H13A | 0.7230 | −0.2939 | 0.1209 | 0.120* | |
H13B | 0.7938 | −0.4339 | 0.0519 | 0.120* | |
H13C | 0.9131 | −0.3229 | 0.0561 | 0.120* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N2 | 0.0466 (16) | 0.0427 (13) | 0.0422 (14) | 0.0025 (11) | −0.0123 (12) | −0.0088 (10) |
N3 | 0.0497 (17) | 0.0534 (14) | 0.0479 (15) | −0.0011 (13) | −0.0106 (13) | −0.0165 (11) |
O3 | 0.0696 (17) | 0.0648 (13) | 0.0544 (14) | 0.0067 (12) | −0.0116 (12) | −0.0051 (10) |
C6 | 0.049 (2) | 0.0403 (15) | 0.0454 (17) | 0.0008 (14) | −0.0183 (15) | −0.0089 (13) |
C10 | 0.046 (2) | 0.0418 (16) | 0.0518 (19) | 0.0017 (14) | −0.0195 (16) | −0.0124 (14) |
C3 | 0.050 (2) | 0.0474 (16) | 0.0463 (18) | 0.0025 (14) | −0.0161 (15) | −0.0150 (13) |
C4 | 0.069 (2) | 0.0499 (16) | 0.0403 (16) | 0.0040 (16) | −0.0168 (16) | −0.0073 (13) |
O2 | 0.0814 (19) | 0.0733 (15) | 0.0530 (15) | 0.0150 (13) | −0.0145 (14) | −0.0142 (12) |
C5 | 0.063 (2) | 0.0435 (16) | 0.0499 (19) | 0.0003 (15) | −0.0160 (17) | −0.0061 (13) |
N1 | 0.0588 (19) | 0.0493 (13) | 0.0455 (14) | 0.0120 (13) | −0.0159 (13) | −0.0103 (11) |
O1 | 0.093 (2) | 0.0765 (15) | 0.0464 (14) | 0.0227 (14) | −0.0069 (12) | −0.0092 (11) |
C7 | 0.055 (2) | 0.0464 (17) | 0.063 (2) | 0.0073 (15) | −0.0226 (17) | −0.0115 (14) |
C12 | 0.061 (2) | 0.0537 (18) | 0.052 (2) | −0.0009 (17) | −0.0167 (18) | −0.0058 (15) |
C8 | 0.054 (2) | 0.0514 (17) | 0.065 (2) | 0.0060 (16) | −0.0167 (18) | −0.0213 (15) |
C1 | 0.062 (2) | 0.0562 (19) | 0.063 (2) | 0.0124 (17) | −0.0070 (18) | −0.0096 (16) |
C9 | 0.047 (2) | 0.0543 (18) | 0.0519 (19) | −0.0030 (15) | −0.0084 (16) | −0.0209 (15) |
C11 | 0.068 (3) | 0.079 (2) | 0.070 (2) | 0.007 (2) | −0.007 (2) | −0.0303 (18) |
C2 | 0.052 (2) | 0.0570 (18) | 0.0480 (19) | 0.0035 (16) | −0.0085 (16) | −0.0122 (15) |
C13 | 0.083 (3) | 0.076 (2) | 0.064 (2) | 0.000 (2) | −0.024 (2) | 0.0049 (18) |
N2—C3 | 1.315 (3) | O1—C2 | 1.211 (3) |
N2—C10 | 1.365 (3) | C7—C8 | 1.344 (4) |
N3—C9 | 1.322 (3) | C7—H7A | 0.9300 |
N3—C10 | 1.353 (3) | C12—C13 | 1.497 (4) |
O3—C12 | 1.310 (3) | C8—C9 | 1.413 (4) |
O3—H3A | 0.8200 | C8—H8A | 0.9300 |
C6—C5 | 1.399 (4) | C1—C2 | 1.498 (4) |
C6—C7 | 1.402 (4) | C1—H1B | 0.9600 |
C6—C10 | 1.414 (3) | C1—H1C | 0.9600 |
C3—N1 | 1.397 (3) | C1—H1D | 0.9600 |
C3—C4 | 1.426 (4) | C9—C11 | 1.489 (4) |
C4—C5 | 1.364 (4) | C11—H11A | 0.9600 |
C4—H4A | 0.9300 | C11—H11B | 0.9600 |
O2—C12 | 1.195 (3) | C11—H11C | 0.9600 |
C5—H5A | 0.9300 | C13—H13A | 0.9600 |
N1—C2 | 1.371 (3) | C13—H13B | 0.9600 |
N1—H1A | 0.8600 | C13—H13C | 0.9600 |
C3—N2—C10 | 118.3 (2) | C7—C8—C9 | 119.2 (3) |
C9—N3—C10 | 117.6 (2) | C7—C8—H8A | 120.4 |
C12—O3—H3A | 109.5 | C9—C8—H8A | 120.4 |
C5—C6—C7 | 125.0 (3) | C2—C1—H1B | 109.5 |
C5—C6—C10 | 118.0 (2) | C2—C1—H1C | 109.5 |
C7—C6—C10 | 117.0 (3) | H1B—C1—H1C | 109.5 |
N3—C10—N2 | 115.3 (2) | C2—C1—H1D | 109.5 |
N3—C10—C6 | 123.0 (2) | H1B—C1—H1D | 109.5 |
N2—C10—C6 | 121.7 (3) | H1C—C1—H1D | 109.5 |
N2—C3—N1 | 114.4 (2) | N3—C9—C8 | 123.1 (3) |
N2—C3—C4 | 124.0 (2) | N3—C9—C11 | 116.5 (3) |
N1—C3—C4 | 121.7 (3) | C8—C9—C11 | 120.4 (3) |
C5—C4—C3 | 117.3 (3) | C9—C11—H11A | 109.5 |
C5—C4—H4A | 121.3 | C9—C11—H11B | 109.5 |
C3—C4—H4A | 121.3 | H11A—C11—H11B | 109.5 |
C4—C5—C6 | 120.7 (3) | C9—C11—H11C | 109.5 |
C4—C5—H5A | 119.7 | H11A—C11—H11C | 109.5 |
C6—C5—H5A | 119.7 | H11B—C11—H11C | 109.5 |
C2—N1—C3 | 129.4 (2) | O1—C2—N1 | 124.0 (3) |
C2—N1—H1A | 115.3 | O1—C2—C1 | 122.8 (3) |
C3—N1—H1A | 115.3 | N1—C2—C1 | 113.3 (3) |
C8—C7—C6 | 120.1 (3) | C12—C13—H13A | 109.5 |
C8—C7—H7A | 120.0 | C12—C13—H13B | 109.5 |
C6—C7—H7A | 120.0 | H13A—C13—H13B | 109.5 |
O2—C12—O3 | 123.8 (3) | C12—C13—H13C | 109.5 |
O2—C12—C13 | 123.9 (3) | H13A—C13—H13C | 109.5 |
O3—C12—C13 | 112.2 (3) | H13B—C13—H13C | 109.5 |
C9—N3—C10—N2 | −179.5 (3) | C7—C6—C5—C4 | 179.3 (3) |
C9—N3—C10—C6 | 0.7 (4) | C10—C6—C5—C4 | −1.1 (5) |
C3—N2—C10—N3 | −179.2 (3) | N2—C3—N1—C2 | −170.8 (3) |
C3—N2—C10—C6 | 0.6 (4) | C4—C3—N1—C2 | 10.3 (5) |
C5—C6—C10—N3 | −179.7 (3) | C5—C6—C7—C8 | 179.0 (3) |
C7—C6—C10—N3 | 0.0 (4) | C10—C6—C7—C8 | −0.6 (5) |
C5—C6—C10—N2 | 0.6 (4) | C6—C7—C8—C9 | 0.6 (5) |
C7—C6—C10—N2 | −179.8 (3) | C10—N3—C9—C8 | −0.7 (4) |
C10—N2—C3—N1 | 179.9 (3) | C10—N3—C9—C11 | 179.8 (3) |
C10—N2—C3—C4 | −1.3 (5) | C7—C8—C9—N3 | 0.0 (5) |
N2—C3—C4—C5 | 0.8 (5) | C7—C8—C9—C11 | 179.5 (3) |
N1—C3—C4—C5 | 179.5 (3) | C3—N1—C2—O1 | −2.5 (5) |
C3—C4—C5—C6 | 0.5 (5) | C3—N1—C2—C1 | 177.9 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3A···N2i | 0.82 | 1.96 | 2.774 (3) | 173 |
N1—H1A···O2ii | 0.86 | 2.07 | 2.931 (3) | 178 |
Symmetry codes: (i) x+1, y−1, z; (ii) x−1, y+1, z. |
Experimental details
Crystal data | |
Chemical formula | C11H11N3O·C2H4O2 |
Mr | 261.28 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 8.3628 (17), 9.0904 (18), 9.5093 (19) |
α, β, γ (°) | 71.30 (3), 76.43 (3), 78.64 (3) |
V (Å3) | 659.8 (2) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.15 × 0.10 × 0.07 |
Data collection | |
Diffractometer | Rigaku R-AXIS RAPID diffractometer |
Absorption correction | Multi-scan (ABSCOR; Higashi, 1995) |
Tmin, Tmax | 0.986, 0.993 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5757, 2591, 1014 |
Rint | 0.058 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.047, 0.160, 0.91 |
No. of reflections | 2591 |
No. of parameters | 172 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.21, −0.20 |
Computer programs: PROCESS-AUTO (Rigaku, 1998), CrystalStructure (Rigaku/MSC, 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3A···N2i | 0.82 | 1.96 | 2.774 (3) | 173.1 |
N1—H1A···O2ii | 0.86 | 2.07 | 2.931 (3) | 178.2 |
Symmetry codes: (i) x+1, y−1, z; (ii) x−1, y+1, z. |
Acknowledgements
The authors acknowledge support from the `Spring Sunshine' Plan of the Ministry of Education of China (grant No. Z2011125) and the National Natural Science Foundation of China (grant No. 21262049)
References
Badawneh, M., Ferrarini, P. L., Calderone, V., Manera, C., Martinotti, E., Mori, C., Saccomanni, G. & Testai, L. (2001). Eur. J. Med. Chem. 36, 925–934. Web of Science CrossRef PubMed CAS Google Scholar
Brandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Brown, E. V. (1965). J. Org. Chem. 30, 1607–1610. CrossRef CAS Web of Science Google Scholar
Capozzi, A., Mantuano, E., Matarrese, P., Saccomanni, G., Manera, C., Mattei, V., Gambardella, L., Malorni, W., Sorice, M. & Misasi, R. (2012). Anticancer Agents Med. Chem. 12, 653–662. CrossRef CAS PubMed Google Scholar
Gan, X., Chi, S. M., Mu, W. H., Yao, J. C., Quan, L., Li, C., Bian, Z. Y., Chen, Y. & Fu, W. F. (2011). Dalton Trans. 40, 7365–7374. Web of Science CSD CrossRef CAS PubMed Google Scholar
Henry, R. A. & Hammond, P. R. (1977). J. Heterocycl. Chem. pp. 1109–1114. CAS Google Scholar
Higashi, T. (1995). ABSCOR. Rigaku Corporation, Tokyo, Japan. Google Scholar
Li, Z. X., Li, C., Mu, W. H., Xiong, S. X. & Fu, W. F. (2011). Inorg. Chim. Acta, 379, 7–15. Web of Science CSD CrossRef CAS Google Scholar
Nagasawa, J. Y., Song, J., Chen, H., Kim, H. W., Blazel, J., Ouk, S., Groschel, B., Borges, V., Ong, V., Yeh, L. T., Girardet, J. L., Vernier, J. M., Raney, A. K. & Pinkerton, A. B. (2011). Bioorg. Med. Chem. Lett. 21, 760–763. Web of Science CrossRef CAS PubMed Google Scholar
Rigaku (1998). PROCESS-AUTO. Rigaku Corporation, Tokyo, Japan. Google Scholar
Rigaku/MSC (2006). CrystalStructure. Rigaku/MSC, The Woodlands, Texas, USA. Google Scholar
Roma, G., Braccio, M. D., Grossi, G., Mattioli, F. & Ghia, M. (2000). Eur. J. Med. Chem. 35, 1021–1026. Web of Science CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sivakumar, P., Iyer, G. & Doble, M. (2011). Med. Chem. Res. pp. 1–8. Google Scholar
Zong, R. F., Naud, F., Segal, C., Burke, J., Wu, F. Y. & Thummel, R. (2004). Inorg. Chem. 43, 6195–6202. Web of Science CSD CrossRef PubMed CAS Google Scholar
Zúñiga, C., Moya, S. A., Fuentealba, M., Aranda, B. & Aguirre, P. (2011). Inorg. Chem. Commun. 14, 964–967. Google Scholar
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The structure and chemical properties of the 1,8-naphthyridine ring system are interesting to both synthetic and pharmaceutical organic chemists. They can act as monodendate, chelating bidendate and dinuclear bridging ligands(Zong et al., 2004; Zúñiga et al., 2011; Li et al., 2011; Gan et al., 2011). They have also found use as anti-bacterial(Sivakumar et al., 2011), anti-inflammatory(Roma et al., 2000), anti-hypertensive(Badawneh et al., 2001) and anti-cancer drugs(Nagasawa et al., 2011; Capozzi et al., 2012). Herein we report the synthesis and structure of the title co-crystal, C11H11N3O.C2H4O2.
The structure of the title complex is shown in Fig. 1 and Fig. 2 and the hydrogen-bond geometry is given in Table. 1. The planes defined by 7-acetamino-2–methyl-1,8-naphthyridine and acetic acid have root mean square (r.m.s.) deviations of 0.0720 Å and 0.0014 Å and the angle between the planes is 8.66 (19) °. There are two, O—H···N and N—H···O, intermolecular hydrogen bonds between 7-acetamino-2-methyl-1,8-naphthyridine and acetic acid, which link the molecules to form layered units. The O(3)···N(2) and N(1)···O(2) distances are 2.782 (4) and 2.941 (4) Å and the angles O(3)—H(3A)···N(2) and N(1)—H(1A)···O(2) are 173.1 (4)° and 178.0 (2)°. The complementarity of the hydrogen-bonding interactions make the hydrogen-bonded units stable. The stability of these units may explain the difficulty in separating the two components via chromatography. The distances between the adjacent parallel planes are 2.960 (4) and 3.349 (4) Å. The weak C—H···N contacts have a H···N distance of 2.666 (3) Å.