### Abstract

Mid-infrared, far-infrared, and Raman vibrational spectroscopic studies were combined with density functional theory (DFT) calculations and normal coordinate force field analyses for N,N'-dimethylurea (DMU), N,N,N',N'-tetramethylurea (TMU), and N,N'-dimethylpropyleneurea (DMPU: IUPAC name 1,3-dimethyltetrahydropyrimidin-2(1H)-one). The equilibrium molecular geometry of DMU (all three conformers), TMU, and DMPU and the frequencies, intensities, and depolarization ratios of their fundamental infrared (IR) and Raman vibrational transitions were obtained by DFT calculations. The vibrational spectra were fully analyzed by normal coordinate methods as well. A starting force field for DMPU was obtained by adapting corresponding force constants for DMU and TMU, resulting after refinements in the stretching force constants C=O (7.69, 7.30, 7.68 N·cm^{-1}), C-N (5.16, 5.55, 5.05N·cm^{-1}), and C-Me (5.93, 4.00, 4.22 N·cm ^{-1}) for DMU, TMU, and DMPU, respectively. The dominating conformer of liquid DMU was identified as trans-trans, strong intermolecular hydrogen bonding was verified in solid DMU, and weak dipole-dipole association was found in liquid TMU and in DMPU. Special attention was paid to analyzing the methyl group frequencies, which revealed deviations from local C3v symmetry. A linear correlation was found between the CH stretching force constants and the inverse of the CH bond lengths (1/r2). The averaged NH stretching frequencies of gaseous, dissolved, and solid urea and of DMU, with variations for hydrogen bonding of different strength, are linearly correlated to the NH stretching force constants. Characteristic skeletal vibrations were assigned for a broad variety of urea derivatives and also for pyrimidine derivatives, which all contain the N2C=O entity. The very strong IR bands of C=O stretching (1,676 ± 40 cm^{-1}) and asymmetric CN2 stretching (1,478 ± 60 cm^{-1}), and the very intense Raman feature of symmetric CN2 stretching or ring breathing (757 80 cm^{-1}), can be recognized as fingerprint bands also for the pyrimidine derivatives cytosine, thymine, and uracil, which all are nucleobases in DNA and RNA nucleotides.

Original language | English |
---|---|

Pages (from-to) | 274-326 |

Number of pages | 53 |

Journal | Applied Spectroscopy Reviews |

Volume | 45 |

Issue number | 4 |

DOIs | |

Publication status | Published - Jul 2010 |

### Fingerprint

### Keywords

- equilibrium geometry
- hydrogen bonding
- N,N'-dimethylpropyleneurea
- N,N'-dimethylurea
- N,N,N',N'-tetramethylurea
- theoretical calculations
- urea
- Vibrational spectra

### ASJC Scopus subject areas

- Spectroscopy
- Instrumentation

### Cite this

*Applied Spectroscopy Reviews*,

*45*(4), 274-326. https://doi.org/10.1080/05704928.2010.483670

**Vibrational spectroscopic and theoretical studies of urea derivatives with biochemical interest : N,N'-dimethylurea, N,N,N',N'-tetramethylurea, and N,N'-dimethylpropyleneurea.** / Mink, J.; Hajba, László; Pápai, I.; Mihály, J.; Neméth, Csaba; Skripkin, Mikhail Yu; Sandström, Magnus.

Research output: Contribution to journal › Article

*Applied Spectroscopy Reviews*, vol. 45, no. 4, pp. 274-326. https://doi.org/10.1080/05704928.2010.483670

}

TY - JOUR

T1 - Vibrational spectroscopic and theoretical studies of urea derivatives with biochemical interest

T2 - N,N'-dimethylurea, N,N,N',N'-tetramethylurea, and N,N'-dimethylpropyleneurea

AU - Mink, J.

AU - Hajba, László

AU - Pápai, I.

AU - Mihály, J.

AU - Neméth, Csaba

AU - Skripkin, Mikhail Yu

AU - Sandström, Magnus

PY - 2010/7

Y1 - 2010/7

N2 - Mid-infrared, far-infrared, and Raman vibrational spectroscopic studies were combined with density functional theory (DFT) calculations and normal coordinate force field analyses for N,N'-dimethylurea (DMU), N,N,N',N'-tetramethylurea (TMU), and N,N'-dimethylpropyleneurea (DMPU: IUPAC name 1,3-dimethyltetrahydropyrimidin-2(1H)-one). The equilibrium molecular geometry of DMU (all three conformers), TMU, and DMPU and the frequencies, intensities, and depolarization ratios of their fundamental infrared (IR) and Raman vibrational transitions were obtained by DFT calculations. The vibrational spectra were fully analyzed by normal coordinate methods as well. A starting force field for DMPU was obtained by adapting corresponding force constants for DMU and TMU, resulting after refinements in the stretching force constants C=O (7.69, 7.30, 7.68 N·cm-1), C-N (5.16, 5.55, 5.05N·cm-1), and C-Me (5.93, 4.00, 4.22 N·cm -1) for DMU, TMU, and DMPU, respectively. The dominating conformer of liquid DMU was identified as trans-trans, strong intermolecular hydrogen bonding was verified in solid DMU, and weak dipole-dipole association was found in liquid TMU and in DMPU. Special attention was paid to analyzing the methyl group frequencies, which revealed deviations from local C3v symmetry. A linear correlation was found between the CH stretching force constants and the inverse of the CH bond lengths (1/r2). The averaged NH stretching frequencies of gaseous, dissolved, and solid urea and of DMU, with variations for hydrogen bonding of different strength, are linearly correlated to the NH stretching force constants. Characteristic skeletal vibrations were assigned for a broad variety of urea derivatives and also for pyrimidine derivatives, which all contain the N2C=O entity. The very strong IR bands of C=O stretching (1,676 ± 40 cm-1) and asymmetric CN2 stretching (1,478 ± 60 cm-1), and the very intense Raman feature of symmetric CN2 stretching or ring breathing (757 80 cm-1), can be recognized as fingerprint bands also for the pyrimidine derivatives cytosine, thymine, and uracil, which all are nucleobases in DNA and RNA nucleotides.

AB - Mid-infrared, far-infrared, and Raman vibrational spectroscopic studies were combined with density functional theory (DFT) calculations and normal coordinate force field analyses for N,N'-dimethylurea (DMU), N,N,N',N'-tetramethylurea (TMU), and N,N'-dimethylpropyleneurea (DMPU: IUPAC name 1,3-dimethyltetrahydropyrimidin-2(1H)-one). The equilibrium molecular geometry of DMU (all three conformers), TMU, and DMPU and the frequencies, intensities, and depolarization ratios of their fundamental infrared (IR) and Raman vibrational transitions were obtained by DFT calculations. The vibrational spectra were fully analyzed by normal coordinate methods as well. A starting force field for DMPU was obtained by adapting corresponding force constants for DMU and TMU, resulting after refinements in the stretching force constants C=O (7.69, 7.30, 7.68 N·cm-1), C-N (5.16, 5.55, 5.05N·cm-1), and C-Me (5.93, 4.00, 4.22 N·cm -1) for DMU, TMU, and DMPU, respectively. The dominating conformer of liquid DMU was identified as trans-trans, strong intermolecular hydrogen bonding was verified in solid DMU, and weak dipole-dipole association was found in liquid TMU and in DMPU. Special attention was paid to analyzing the methyl group frequencies, which revealed deviations from local C3v symmetry. A linear correlation was found between the CH stretching force constants and the inverse of the CH bond lengths (1/r2). The averaged NH stretching frequencies of gaseous, dissolved, and solid urea and of DMU, with variations for hydrogen bonding of different strength, are linearly correlated to the NH stretching force constants. Characteristic skeletal vibrations were assigned for a broad variety of urea derivatives and also for pyrimidine derivatives, which all contain the N2C=O entity. The very strong IR bands of C=O stretching (1,676 ± 40 cm-1) and asymmetric CN2 stretching (1,478 ± 60 cm-1), and the very intense Raman feature of symmetric CN2 stretching or ring breathing (757 80 cm-1), can be recognized as fingerprint bands also for the pyrimidine derivatives cytosine, thymine, and uracil, which all are nucleobases in DNA and RNA nucleotides.

KW - equilibrium geometry

KW - hydrogen bonding

KW - N,N'-dimethylpropyleneurea

KW - N,N'-dimethylurea

KW - N,N,N',N'-tetramethylurea

KW - theoretical calculations

KW - urea

KW - Vibrational spectra

UR - http://www.scopus.com/inward/record.url?scp=77953757322&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77953757322&partnerID=8YFLogxK

U2 - 10.1080/05704928.2010.483670

DO - 10.1080/05704928.2010.483670

M3 - Article

VL - 45

SP - 274

EP - 326

JO - Applied Spectroscopy Reviews

JF - Applied Spectroscopy Reviews

SN - 0570-4928

IS - 4

ER -