I. INTRODUCTION
Menthyl lactate is a kind of mint derivatives, and it has advantages in mild and persistent freshening action and cooling on human skin (Erman, Reference Erman2007). As shown in Figure 1, menthyl lactate (C13H24O3), systematic name (1R,2S,5R)-2-isopropyl-5-methylcyclohexyl(S)-2-hydroxypropionate, with the CAS register number of 61597-98-6. It was tentatively used in personal care products such as shower gel, skin care lotion, and toilet powder freshener (Xie et al., Reference Xie, She, Feng, Nie and Jiang2009).
Although the compound has been on the market for a long time, the crystal structure of menthyl lactate by single-crystal diffraction or powder diffraction has not been reported in the literature so far.
Figure 1. Structural formula of menthyl lactate.
II. EXPERIMENTAL
A. Sample preparation
The title compound (98% purity) was purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan) and identified by the Fourier transform infrared spectroscopy (Figure S1) along with an elemental analysis. The elemental analysis showed that the content of C, H, and O were 68.70, 12.09, and 19.21%, respectively. The sample (ρ = 0.99 g cm−3, T melt = 44–46 °C) was ground into powder and sieved through 300-mesh screening.
B. Diffraction data collection and reduction
The X-ray powder diffraction (XRD) data were recorded at room temperature using an X'Pert PRO diffractometer (PANalytical Co., Ltd., Netherlands) with a PIXcel 1D detector and CuKα 1 radiation (λ = 1.540 56 Å, generator setting: 40 kV and 40 mA). The diffractometer was operated in the angular range from 4° to 50°2θ with a step size of 0.013 13°2θ and a counting time of 30 ms step−1. The experimental XRD pattern is depicted in Figure 2. The measurement was performed at a controlled relative humidity level of 60%.
Figure 2. X-ray powder diffraction pattern of menthyl lactate, using CuKα 1 radiation (λ = 1.540 56 Å).
Data evaluation was performed using the Reflex module in the software package Material Studio 4.2 (Accelrys Co., Ltd., USA). The first stage involves the pretreatment of XRD pattern by correcting the baseline, subtracting the background, smoothing, and eliminating the Kα 2 component before the indexing (Li et al., Reference Li, Wu, Pan, Cheng and Li2014). Automatic indexing of the pretreated experimental XRD pattern was done using DICVOL91 (LoueÈr and LoueÈr, Reference LoueÈr and LoueÈr1972; Boultif and LoueÈr, Reference Boultif and LoueÈr1991) and then the indexing result was refined using the Pawley method (Pawley, Reference Pawley1981). The final R wp of the structure in the Pawley refinement was converged at 9.37%.
III. RESULTS
The experimental XRD pattern is depicted in Figure 2. Indexing results confirmed that menthyl lactate is triclinic with space group P−1 and unit-cell parameters after the Pawley refinement are [a = 5.522(6) Å, b = 11.795(8) Å, c = 17.780(6) Å, α = 50.632(3)°, β = 90.000(0)°, γ = 117.632(4)°, unit-cell volume V = 716.392(0) Å3, and Z = 2]. Table I gives the 2θ, d-spacing, relative intensity, and hkl for each observed line. The calculation results of the XRD figure show that the merits are F 13 = 42.5 (0.0091, 34) (Smith and Snyder, Reference Smith and Snyder1979) and M 13 = 23.8 (de Wolff, Reference de Wolff1968). All lines were indexed and are consistent with the P−1 space group.
Table I. XRD data of menthyl lactate
All measured lines were indexed. The d-values were calculated using CuKα 1 radiation (λ = 1.540 56 Å).
SUPPLEMENTARY MATERIAL
The supplementary material for this article can be found at http://dx.doi.org/10.1017/S0885715616000439.
ACKNOWLEDGEMENT
The authors acknowledge the financial support from China Tobacco Yunnan Industrial Co., Ltd. (Grant No. 2014H1069).
