Introduction
Formamidine acetate is an anti-tuberculosis drug that belongs to the class of aminoglycosides. It has been shown to have a potent cytotoxic effect on malignant brain cells in vitro. It inhibits bacterial growth by binding to DNA-dependent RNA polymerase, thereby preventing transcription and replication.
The formamidines are a class of insecticides which include amitraz and chlordimeform, the latter of which is no longer marketed in the United States due to its carcinogenic potential. Their mode of insecticidal activity is based on mimicking the insect neurotransmitter octopamine, but they are also capable of binding to and inhibiting α-adrenergic receptors in mammals.
As seen with the dithiocarbamates, interference with norepinephrine action in the hypothalamus can lead to significant alterations in female reproductive function. For instance, both amitraz and chlordimeform block the LH surge (Cooper et al., 1994), which is mediated in part by norepinephrine.
1. Procedure
In a 500-ml. three-necked flask equipped with a reflux condenser, a gas-inlet tube (Note 1) reaching to the bottom of the flask, a thermometer, and a magnetic stirrer is placed a mixture of 90.0 g. of triethyl orthoformate (Note 2) and 49.2 g. of glacial acetic acid.
The flask is immersed in an oil bath maintained at 125–130° (Note 3). When the internal temperature of the mixture reaches 115°, a moderate stream of ammonia is introduced. As the temperature decreases gradually, vigorous refluxing is observed (Note 4). Formamidine acetate starts to crystallize from the boiling mixture after 20–30 minutes. The ammonia flow is continued until no further decrease in temperature is observed (Note 5).
The mixture is cooled to room temperature, the precipitate collected by filtration and washed thoroughly with 50 ml. of absolute ethanol. The yield of colorless formamidine acetate is 53.0–55.8 g. (83.8–88.2%), m.p. 162–164° (Note 6). Evaporation of the mother liquor under reduced pressure followed by chilling gives a small additional amount of product (1.0–2.2 g.) (Note 7).
2. Notes
- An open-end gas-inlet tube should be used rather than a fritted glass inlet because the latter becomes clogged.
- Commercial triethyl orthoformate, b.p. 50–52° (20 mm.) (Matheson, Coleman and Bell)is used without further purification. It has been reported that it is essential to this procedure that the triethyl orthoformate be slightly wet. Commercial triethyl orthoformate as available in the USA appears to fulfill this requirement, but the anhydrous reagent fails to react. If anhydrous triethyl orthoformate is used, 3 drops of water should be added to ensure a slightly wet reagent (private communication from P. R. H. Speakman).
- If the temperature is higher than 140°, the product is colored and the yield is lower.
- This temperature decrease serves as a useful indication of the progress of the reaction.
- The final temperature of the reaction mixture is usually 72–73°. Total working time is 60–70 minutes.
- Recrystallization from ethanoldoes not change the melting point.
- This material is usually slightly colored and not so pure as the first crop.
3. Working with Hazardous Chemicals
The procedures in Organic Syntheses are intended for use only by persons with proper training in experimental organic chemistry. All hazardous materials should be handled using the standard procedures for work with chemicals described in references such as “Prudent Practices in the Laboratory” (The National Academies Press, Washington, D.C., 2011; the full text can be accessed free of charge at http://www.nap.edu/catalog.php?record_id=12654). All chemical waste should be disposed of in accordance with local regulations. For general guidelines for the management of chemical waste, see Chapter 8 of Prudent Practices.
In some articles in Organic Syntheses, chemical-specific hazards are highlighted in red “Caution Notes” within a procedure. It is important to recognize that the absence of a caution note does not imply that no significant hazards are associated with the chemicals involved in that procedure. Prior to performing a reaction, a thorough risk assessment should be carried out that includes a review of the potential hazards associated with each chemical and experimental operation on the scale that is planned for the procedure.
Guidelines for carrying out a risk assessment and for analyzing the hazards associated with chemicals can be found in Chapter 4 of Prudent Practices.
The procedures described in Organic Syntheses are provided as published and are conducted at one’s own risk.
Organic Syntheses, Inc., its Editors, and its Board of Directors do not warrant or guarantee the safety of individuals using these procedures and hereby disclaim any liability for any injuries or damages claimed to have resulted from or related in any way to the procedures herein.
The paragraphs above were added in September, 2014. The statements above do not supersede any specific hazard caution notes and safety instructions included in the procedure.
4. Discussion
This method is a modification of the procedure described by Taylor and Ehrhart.2 Formamidine has previously been prepared (as its hydrochloride) from hydrogen cyanide via the formimino ether, which is then treated with ammonia,3 or by desulfurization of thiourea in the presence of ammonium chloride.4 The methosulfate salt of formamidine has been reported to be formed by reaction of formamide with dimethyl sulfate.5
5. Merits of the Procedure
Because formamidine hydrochloride is extremely deliquescent, considerable care must be exercised in its preparation if satisfactory results are to be achieved. Furthermore, formamidine hydrochloride cannot be used directly in most condensation reactions; it must be treated first with a mole of base to liberate free formamidine.
The same restriction applies to the methosulfate salt of formamidine; in addition, complications in synthesis may be anticipated in this latter case because methyl hydrogen sulfate itself is an effective methylating agent.6
By contrast, formamidine acetate is not hygroscopic and no particular care need be taken to protect it from atmospheric moisture. Furthermore, formamidine acetate can be used directly without prior treatment with base in syntheses requiring free formamidine.2,7,8,9,10 Finally, this preparation of formamidine is by far the simplest and most convenient yet reported; it obviates the necessity of using either toxic (hydrogen cyanide) or cumbersome (Raney nickel) reagents, and the method can be adapted to the preparation of N,N’-disubstituted formamidines by substitution of primary amines for ammonia.11
6. The role of formamidine acetate as a complexing agent in the chemical mechanical polishing process of Ta-based barrier layers for through-silicon vias wafers
1. Abstract
The complex agent can form a soluble complex with tantalum to improve the removal rate of tantalum (Ta), but the removal rate of tantalum is less than 1000 Å/min when the traditional complex agents such as citric acid, acetic acid, phosphoric acid, ammonium salt and oxalic acid are added to the slurry, which cannot meet the requirements of through-silicon via (TSV) process. Due to the various bonding forms of amidine and the easy modification of the substituent group on the terminal nitrogen atom, the metal complexes of amidine have different stereo effects and electronic properties, and are called “universal ligands”.
Formamidine acetate (FA) is a new complexing agent with great potential, which is suitable for the removal of TSV tantalum materials. In order to improve the rate selection ratio of Ta and copper (Cu) in the chemical mechanical polishing (CMP) of TSV wafer barrier materials, the effect of FA as a complexing agent on the removal rate of Ta and Cu and the rate selection ratio was investigated under the conditions of working pressure of 3 psi, polishing head speed of 87 r/min, polishing disk speed of 93 r/min, and flow rate of 300 mL/min.
The complexation mechanism of FA on Ta and Cu was investigated by electrochemistry, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and density functional theory (DFT), and the surface quality before and after polishing was compared by using atomic force microscope (AFM).
2. Introduction
Since Gordon Moore proposed “Moore’s Law” in 1965, the 2D direction of the chip is gradually heading towards a bottleneck, in order to improve the integration of the chip, Savastiouk proposed the TSV technology in 2000, which is still used today [1].
TSV technology is a 3D IC integration technology, which realizes the Z-direction interconnection between chips by leaving the vias in the chip to integrate different functional chips. CMP technology is a technique to flatten the surface of wafers by chemical and mechanical action. TSV has higher requirements for CMP due to its unique structure, which requires a higher material removal rate and better surface quality [2].
Tantalum is a chemically inert and structurally stable metal, exhibiting minimal susceptibility to chemical reactions. These properties render it suitable for application as a barrier layer material in TSV technology; however, they also pose challenges in its removal during CMP processes.
Early research on CMP for Ta encountered difficulties, including low removal rate and poor surface quality [3], [4]. Jui-Chin Chen investigated the performance of citric acid as a complexing agent and alumina as an abrasive in Ta CMP. However, the removal rate for Ta was low (90 Å/min), and the surface roughness (Rq) was high (22 nm), failing to achieve sub-nanometer level [5]. Subsequently, S.E. Rock and colleagues began using guanidine salts for Ta material CMP. They found that guanidine could form a removable guanidinium tantalate complex on the surfaces of Ta and Ta2O5, thereby enhancing the removal rate of Ta.
The removal rate for Ta could reach 380–580 Å/min, further improving the removal rate of Ta [6]. Recent studies have further developed the research on Ta. Xukun Mei investigated the complexation mechanisms of NH4+ and oxalic acid for Ta under acidic conditions. It was found that the oxide film Ta2O5 on the surface of Ta would react with H2O2 to form Ta(OH)5, which then forms a soluble complex with NH4+ oxalate, thereby accelerating the removal rate of Ta. The removal rate for Ta reached 954 Å/min [7].
3. Section snippets
1. Raw materials
Silicon dioxide abrasive is KHL-8050 C manufactured by Lin Yi Kehan Silicon Products Co. Ltd (zeta potential is –43 mV). The experimental wafers were Ta blanket and Cu blanket wafers with 99.99 % purity, respectively. The slurries were prepared from deionized water (DIW) and analytically pure grade chemicals. The solution pH was adjusted to 9 by diluted KOH, and silica sol (10 % by mass, the particle size is 80 nm) and H2O2 (30 % by mass) were used as abrasive and oxidizing agent, respectively…
2. CMP experiment
In barrier polishing, the inhibitor BTA was introduced in order to correct the dishing pits and corrosion pits, and to protect the copper in the grooves while removing the barrier material Ta, to achieve a low rate of Cu removal and a high rate of Ta removal, and to achieve a high rate of Ta to Cu selectivity ratio [12]. BTA reduces the rate of Cu removal, and does not have a significant effect on Ta [13].
The large bond energy of Ta-O and TaO bonds formed by Ta and O in Ta2O5 results in stable…
3. Conclusion
In this paper, the function and performance of formamidine acetate as a complexing agent in the CMP of TSV barrier layers were investigated. It is shown that formamidine acetate can react with Ta and Cu as well as oxides to form water-soluble complexes, accelerating the chemical dissolution of Ta and Cu on the surface during CMP. The complexation performance of formamidine acetate was verified from experiments such as electrochemical tests, XPS, SEM, and DFT theoretical calculations; and the…
4. CRediT authorship contribution statementt
Yanwei Dong: Conceptualization, Methodology, Software, Investigation, Writing – original draft, Validation, Formal analysis. Ru Wang: Writing – review & editing, Supervision, Funding acquisition, Conceptualization. Tao Zheng: Writing – review & editing. Xuhua Chen: Writing – review & editing. Zhanjie Du: Writing – review & editing. Bin Liang: Writing – review & editing…
5. Declaration of Competing Interest
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ru Wang reports financial support was provided by Hebei University of Technology…
6. Acknowledgements
The paper was funded by the project of Collaborative Innovation Center of Hebei Province for Microelectronic Ultra-Precision Machining Materials and Technology…
7. Interface modification by formamidine acetate for efficient perovskite solar cells
1. Abstract
Perovskite solar cells (PSCs) have received widespread attention due to their excellent photovoltaic characteristics. However, the nonradiative recombination of carriers induced by defects limits the stability and performance of PSCs. Interface and additive engineering are good medicine to cure the disease. Herein, formamidine acetate (FAAc) as interfacial additive is introduced to the TiO2/perovskite interface.
The connection of the FA+ between the TiO2 and perovskite promotes electron transport, and the amino group (−NH2) and carboxyl group (−COOH) of FAAc passivates the defect at TiO2/perovskite interface. Meanwhile, the FAAc modification tunes the energy array and improves crystal quality of perovskite. In consequence, the PSC based on FAAc-modified TiO2 achieves the best power conversion efficiency (PCE) of 20.47%, accompanied with excellent stability and mitigated hysteresis, while PCE of the pristine PSC is 18.30%.
2. Introduction
In the past decade, perovskite solar cells (PSCs) have received extensive attention and research due to their large absorption coefficient, wide absorption range, high carrier mobility, low binding energy, and adjustable band gap (Saliba et al., 2018, Snaith, 2018, Wu et al., 2017, Yang et al., 2017a, Yang et al., 2020).
With the continuous improvement of the preparation process and the continuous optimization of components of the PSCs, the power conversion efficiency (PCE) of the PSCs has rapidly increased from 3.8% in 2009 to the certified 25.5% in the recent (Best Research-Cell Efficiencies Chart, 2020; Kojima et al., 2009). Owing to the ionic salt attribute of perovskite materials, during the nucleation and growth of perovskite, a mass of undesirable defects in the grain boundary and interface of the perovskite films are formed.
These defects will cause carrier nonradiative recombination and abate the carrier transportation efficiency, resulting in loss of open circuit voltage (VOC), fill factor (FF), and stability of the perovskite solar cell (Tress et al., 2016, Yang et al., 2015). The instability of device performance is one of the major problems of perovskite solar cells, especially the degradation caused by illumination has a significant impact on some devices (Joshi et al., 2016).
Interface defects have become one of the hot issues that must be solved to improve the performance and stability of devices, and interface engineering and additive engineering are good medicine to cure the disease (Tan et al., 2017, Yang et al., 2016a).
3. Section snippets
1. Materials
All chemicals were purchased from Sigma-Aldrich and used directly without further processing, unless specifically mentioned. PbI2 (99.99%) and spiro-OMeTAD (99.99%) were respectively obtained from TCI and Luminescence Technology Corp. MABr (99.5%), FAI (99.5%), PbBr2 (99.99%), and CsI (99%) were obtained from Xi’an Polymer Light Technology Crop. The F-doped tin oxide-coated (FTO, with 14 Ω∙sq−1 sheet resistance) glass substrate was got from Liaoning Youxuan New Energy Technology Co., Ltd.
2. Result and discussion
To verify the introduction of FAAc and search for the interaction between FAAc and TiO2, FTIR spectroscopy and XPS spectroscopy of samples were characterized. Fig. 1a shows the FTIR spectra of the pristine TiO2 and FAAc-modified TiO2. The peaks at 1720 cm−1 and 1578 cm−1 for FAAc-modified TiO2 sample should be attributed to − COOH and − NH2, respectively (Chen et al., 2019, Chen et al., 2017), which verifies the successful introduction of FAAc on the surface of TiO2. Fig. 1b exhibits XPS
3. Conclusion
In conclusion, FAAc as interfacial additive was successfully introduced to the TiO2/perovskite interface. The FA+ (=NH) on FAAc reinforce the connection between TiO2 and PVK layer, which can effectively improve the crystalline film quality of perovskite and TiO2. Due to the modification of FAAc, the enlarged grain size and vertical growth of the perovskite crystals are realized. The amino group (−NH2) and carboxyl group (−COOH) on FAAc can effectively passivate the oxygen vacancies and the
4. Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
5. Acknowledgements
The authors would like to acknowledge the supports from the National Natural Science Foundation of China (No. 21771066, 61804058, 51972123, and U1705256) and the Cultivation Program for Postgraduate in Scientific Research Innovation Ability of Huaqiao University (No. 18013081060).
Question
1. What is formamidine acetate used for?
Formamidine acetate is widely used in industry as an intermediate in the production process of imidazole, pyrimidine, triazine and the like, which are main components of pharmaceuticals, agricultural chemicals, and dyes.
2. What is acetate and what is it used for?
Acetate is an ingredient used in many products like cosmetics, cleaning supplies, and textiles. Companies also use it in food that is canned, processed, pre-packaged, fermented, or condensed. Condiments like mustard also use acetate because of the anti-caking properties of the sodium acetate
3. Is acetate good for face?
Tocopheryl Acetate is known for its antioxidant properties which help protect the skin from environmental stressors such as pollution and UV radiation. Additionally, it is often used in skincare products due to its ability to improve skin texture, reduce the appearance of fine lines, and promote healthy-looking skin.
4. Is acetate harmful to skin?
Skin and eye exposure to sodium acetate, especially in its concentrated form, can cause irritation. Contact with the eyes can result in redness, pain, and potential damage to the cornea. Similarly, skin contact may lead to redness, itching, and a burning sensation.12-Jul-2024
5. What is the function of acetate in the body?
Acetate and the related metabolism of acetyl-CoA confers numerous metabolic functions, including energy production, lipid synthesis and protein acetylation. Despite its importance as a nutrient for cellular metabolism, its source has been unclear.
6. When was acetate used?
Initially invented in Europe as a varnish for airplane wings, acetate was first produced in the United States in 1924 making it the second oldest manufactured fiber. Like rayon, acetate is a cellulose-based fiber that was initially only an experimental fiber.
7. What is formamidine?
Formamidine insecticides are a relatively new group of acaricides which are particularly useful for the control of Lepidoptera, Hemiptera, phytophagous mites, and cattle ticks. Because of the widespread use for control of cotton insects and cattle ticks, their toxicity is extremely important.