The 1,3-Dimethylurea, with CAS number of 96-31-1, can be called N,N'-Dimethylharnstoff ; N,N'-Dimethylurea ; Symmetric dimethylurea ; sym-Dimethylurea . It is a white crystal, 1,3-Dimethylurea (CAS NO.96-31-1) is an amide. Amides/imides react with azo and diazo compounds to generate toxic gases. Flammable gases are formed by the reaction of organic amides/imides with strong reducing agents. Amides are very weak bases (weaker than water). Imides are less basic yet and in fact react with strong bases to form salts. That is, they can react as acids. Mixing amides with dehydrating agents such as P2O5 or SOCl2 generates the corresponding nitrile. The combustion of these compounds generates mixed oxides of nitrogen (NOx).
Properties of 1,3-Dimethylurea&#;
(1)H bond acceptors: 3; (2)H bond donors: 2; (3)Freely Rotating Bonds: 0; (4)Index of Refraction: 1.413; (5)Molar Refractivity: 23.16 cm3; (6)Molar Volume: 92.8 cm3; (7)Surface Tension: 27.4 dyne/cm; (8)Density: 0.949 g/cm3; (9)Flash Point: 124.3 °C; (10)Enthalpy of Vaporization: 50.71 kJ/mol; (11)Boiling Point: 269 °C at 760 mmHg; (12)Vapour Pressure: 0. mmHg at 25°C; (13)EINECS: 202-498-7; (14)Melting point: 101-104 °C(lit.); (15)Storage temp: Store at RT. ; (16)Water Solubility: 765 g/L (21.5 oC); (17)BRN: ; (18)Polar Surface Area: 23.55 Å2
Structure Descriptors of 1,3-Dimethylurea:
(1)SMILES:O=C(NC)NC;
(2)Std. InChI:InChI=1S/C3H8N2O/c1-4-3(6)5-2/h1-2H3,(H2,4,5,6);
(3)Std. InChIKey:MGJKQDOBUOMPEZ-UHFFFAOYSA-N.
Toxicity of 1,3-Dimethylurea: Organism Test Type Route Reported Dose (Normalized Dose) Effect Source mouse LDLo intraperitoneal mg/kg (mg/kg) BEHAVIORAL: TREMOR
LUNGS, THORAX, OR RESPIRATION: RESPIRATORY DEPRESSION
LUNGS, THORAX, OR RESPIRATION: CYANOSIS Journal of Pharmacology and Experimental Therapeutics. Vol. 54, Pg. 188, . rat LD50 unreported > 2gm/kg (mg/kg) Arzneimittel-Forschung. Drug Research. Vol. 19, Pg. , .
Use of 1,3-Dimethylurea:
1,3-Dimethylurea is used for synthesis of caffeine, theophylline, pharmachemicals, textile aids, herbicides and others. In the textile processing industry 1,3-dimethylurea is used as intermediate for the production of formaldehyde-free easy-care finishing agents for textiles. The estimated world production of DMU is estimated to be less than 25,000 tons.
Polyethylene terephthalate (PET) is a polyester widely used, e.g., for beverage bottles, and textile fabrics, thanks to its chemical and mechanical properties (remarkable impermeability to water and gas, chemical and mechanical resistance, and transparency).
Various solvents can be used for PET chemical recycling and depolymerization into different monomers, thanks to the cleavage of ester groups by solvolysis (hydrolysis, aminolysis, alcoholysis) [ 18 36 ].
Water, glycols, methanol, and amines have already been used for PET transformation into high-value products such as terephthalic acid (TPA), bis(2-hydroxyethyl)terephthalic acid (BHET), mono(2-hydroxyethyl)terephthalic acid (MHET), phenylenediamines, etc.
However, these reactions produce PET monomers with slow reaction rates; the procedure requires high energy and huge volumes of solvents, jointly with complex and expensive purification processes that can hardly be transferred to an industrial scale. Depending on their nature, DESs act as effective solvents and catalysts in PET depolymerization, exhibiting a higher selectivity and faster reactions than ionic liquids or conventional solvolysis, due to the hydrogen bond network favoring the activation of the carbonyl function and thus the nucleophilic attack to the ester moiety [ 37 ].
Lewis acids and bases are compounds that can accept and donate non-bonding electron pairs, respectively. Electron-deficient metals act as Lewis acids when they are capable of binding electron-rich substrates. The presence of metal as an electron pair acceptor in the composition of a DES gives it Lewis acid properties [ 38 ], allowing it to act as a catalyst in various organic reactions, including the chemical pre-treatment of recalcitrant polymers such as lignin [ 39 ].
2 (4:1), urea/Zn(OAc)2·2H2O and urea/Mn(OAc)2·4H2O from 12:1 to 6:1 molar ratios (DESs containing Lewis acids have been used in different reaction conditions to achieve solvolysis of PET [ 40 ]. Wang et al. reported one of the first PET glycolysis by ethylene glycol (EG) in the presence of eutectic mixtures based on urea/ZnCl(4:1), urea/Zn(OAc)·2HO and urea/Mn(OAc)·4HO from 12:1 to 6:1 molar ratios ( Scheme 1 ), affording BHET in high yields (up to 80%) after treatment of PET (pellets) at 170 °C for 30 min [ 37 ].
It was found that when the cation of the metal salt was Zn2+, the change of the anions had no effect on the PET degradation.
On the basis of the proposed mechanism, the coordination between Zn2+ and the oxygen atom of the PET carbonyl increases the polarization of the C=O bond, while the urea interacts with the EG by lengthening the O-H bond and increasing O-nucleophilicity. This favors the addition of the EG to the ester carbonyl, and the solvolysis of PET through the involvement of multiple catalytic active sites.
The treatment required 0.25 g of DES for 5 g of starting polymer. However, one of the drawbacks of this approach is the use of large amounts of water (900 mL) for the workup procedure, which needs to be evaporated at a reduced pressure for the recovery of the product by crystallization.
2 DES, with a BHET yield >80%, calculated by HPLC on an aqueous solution (Very similar conditions and work-up procedures were used by Liu B. et al., [ 41 ] who reported a high conversion (>99%) of PET by 1,3-dimethylurea (1,3-DMU)/Zn(OAc)DES, with a BHET yield >80%, calculated by HPLC on an aqueous solution ( Scheme 2 ).
In this case, the possibility of recycling both DES and EG was also investigated: solvent and catalyst were reused for up to 6 cycles for further depolymerization reactions. ICP-MS analyses revealed a 22% decrease in Zn amount over 6 cycles (with respect to the starting zinc acetate) and a 24% of nitrogen decrease compared to the initial 1,3-DMU.
Some experiments also disclosed the catalytic role of DES in the reaction: by comparing the depolymerization carried out in the presence of ketones or amines as catalysts, PET conversion occurred surprisingly only in the presence of amines, demonstrating that the nitrogen atom could be the &#;catalytic active site&#; of 1,3-DMU.
Additionally, a shrink-core model was employed to establish a correlation between the temperature and the reduction in the volume of spherical PET particles, as determined through kinetic studies.
2 > 0.99) between the volume loss over time at various temperatures. This correlation demonstrates that the optimal reaction conditions were observed at 190 °C, resulting in a complete conversion of PET within 20 min.The Arrhenius plot ( Figure 1 ) reveals a strong linear correlation (R> 0.99) between the volume loss over time at various temperatures. This correlation demonstrates that the optimal reaction conditions were observed at 190 °C, resulting in a complete conversion of PET within 20 min.
2 (1:1, Mp = 146 °C) as a catalyst (Liu L. et al. also investigated the glycolysis of PET with EG, using Betaine/Zn(OAc)(1:1, Mp = 146 °C) as a catalyst ( Scheme 3 ), under experimental conditions close to those of previous work (190 °C, 60 min) [ 42 ].
The selective degradation was efficient for the separation of polyester from cotton fibers, which were recovered without damage after treatment with EG at 190 °C within 45&#;min.
N
-methylethanolamine,N
,N
-dimethylethanolamine) in the PET glycolysis with EG (The authors found that there was a correlation between the degree of nitrogen substitution of HBA and the catalytic activity of Zn-containing DES by using betaine, choline, and other ethanolamine derivatives (-methylethanolamine,-dimethylethanolamine) in the PET glycolysis with EG ( Figure 2 ).
Goto Guangxing to know more.
As a result of the overlapping of NMR spectra, there are different interactions between HBA derivatives and EG: an increasing deshielding of the EG-OH chemical shift was observed in the presence of an increasing number of substituents on the nitrogen atom, with a greater polarization of the O-H bond (higher δ&#; on oxygen) in the interaction with an ammonium salt, and consequently, with a greater propensity of EG to give a nucleophilic substitution during the PET transesterification/glycolysis.
2 DES as catalyst (0.03%w
/w
) for a full conversion in BHET (90% yield) after 40 min at 190 °C (A very efficient DES-catalyzed PET glycolysis with EG was reported by Zhu et al. using a very small amount of 1,5,7-triazabicyclo[4.4.0]dec-5-enium acetate [HTBD(OAc)]/Zn(OAc)DES as catalyst (0.03%) for a full conversion in BHET (90% yield) after 40 min at 190 °C ( Scheme 4 ) [ 43 ].
This new eutectic mixture HTBD(OAc)/Zn(OAc)2 was prepared and characterized, and its catalytic activity was studied by using NMR and computational models for Gibbs energy calculations for each reaction step.
This mechanistic study has revealed the importance of Zn-HTBD ligand cooperation in the synergistic activation of both the PET carbonyl and the hydroxyl of ethylene glycol for an efficient acyl substitution. Moreover, it is worth noting that HTBD(OAc)/Zn(OAc)2 retained its activity after seven cycles of catalytic recycling of PET.
2-based PET depolymerizations, glycolysis with acetamide/ZnCl2 supported on Zeolitic Imidazole Framework type 8 (ZIF-8) was easily carried out at 195 °C for 30 min, with the solid catalyst being removed by filtration and reused in the subsequent reactions (Among other ZnCl-based PET depolymerizations, glycolysis with acetamide/ZnClsupported on Zeolitic Imidazole Framework type 8 (ZIF-8) was easily carried out at 195 °C for 30 min, with the solid catalyst being removed by filtration and reused in the subsequent reactions ( Scheme 5 ) [ 44 ].
The authors described a simple procedure for the catalyst supporting, since the adsorption of DES on ZIF-8 occurred by stirring the single components in absolute ethanol for 8 h, followed by solvent evaporation to afford the active catalyst. The recycling of EG and acetamide/ZnCl2@ZIF-8 was very efficient for up to 6 cycles with a very small erosion of BHET yield.
The advantages of this approach rely not only on the catalyst recycle, but also on the best PET conversion (DES@ZIF-8 conv. 83%, yield BHET 83%) when compared to the yields obtained in the presence of DES and ZIF-8 alone (DES conv. 85% yield BHET 76%; ZIF-8 conv. 72%, yield BHET 72%).
Among other Lewis acid-containing DES, an interesting work was reported by Ciancaleoni et al. for the hydrolysis of PET in Bronsted acids/Lewis acids-DES (BADES) [ 45 ]. In this case, the depolymerization reaction occurred at a much lower temperature (100 °C) than in other methodologies previously reported for PET (160&#;190 °C).
3·6H2O/methanesulfonic acid (MSA) and FeCl3·6H2O/p
-toluensulfonic acid (p
-TSA) were used as eutectic solvents (Moreover, differently from other papers, the used PET flakes deriving from waste plastics can be colored or not, without any differences in the quality of TPA, detected by NMR, IR, and elemental analysis after isolation by precipitation and filtration from an aqueous solution. The higher PET conversions percentages and TPA yields were observed when FeCl·6HO/methanesulfonic acid (MSA) and FeCl·6HO/-toluensulfonic acid (-TSA) were used as eutectic solvents ( Scheme 6 ).
Surprisingly, the ICP mass of the obtained product revealed a very low amount of iron from the eutectic mixture, as low as other heavy metal contaminants already present in the plastic wastes.
The effect of reaction time and temperature heating was also studied and correlated to PET conversion and TPA percentage.
As can be seen from Figure 3 , the required energy to obtain a higher yield in TPA is supplied after 30 min between 80 and 100 °C.
On the other hand, at 100 °C there is an exponential increase in the PET conversion and TPA yield between 20 and 40 min of reaction time because, beyond this time, a plateau of TPA yield is reached that does not increase further after a prolonged treatment up to 5 h.
Another critical point assessed by the authors is the amount of water present in the system and its influence on the success of the reaction. Indeed, the addition of 10 eq of water in FeCl3·6H2O/
p
-TSA and FeCl3·6H2O/MSA leads to a decreasing conversion from 100&#;96.4% to 23.8&#;15.5%, respectively.Finally, the recycling of the system was also carried out by the addition of 300 mg of substrate after each reaction cycle of 1h to evaluate the catalytic capacity of substrate conversion into TPA.
The catalytic system could be reused for four additional runs after the first cycle, revealing that this approach is not only more cost-effective but also environmentally friendly compared to other methods using DES both as catalyst and solvent. This was supported by calculating and comparing the E-factor and Energy Impact with other PET depolymerization methods present in the literature.
For more 1,3-dimethylurea flake factory supplyinformation, please contact us. We will provide professional answers.