Complexes of Urea with Linear Aliphatic Compounds

Zimmerschied, Wilford J.; Dinerstein, R. A.; Weitkamp, A. W.; Marschner, Robert F.

doi:10.1021/ja01176a529

Cited by 32 publications

(12 citation statements)

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“…The minimum amount of RAE required for adduction of enalapril maleate in urea was calculated from the point of intersection of the lines of extrapolation of the initial rate of temperature rise and intermediate final temperature. The second stage of temperature rise is due to displacement of NNAE with RAE, as evidenced by the fact that the overall temperature rise is similar to that of RAE alone (Zimmerschied et al 1949). The minimum ratio of RAE to drug for adduction of enalapril maleate in urea was determined to be 0.446:1.…”

Section: Minimum Ratio Of Rae and Nnae For Inclusion Of Nnae In Ureamentioning

confidence: 94%

“…The minimum amount of RAE required for adduction of enalapril maleate per unit quantity of urea was determined by the modified Zimmerschied calorimetric method (Zimmerschied et al 1949;) based on measurement of temperature rise following addition of increments of RAE to a methanolic solution of urea containing excess of the drug. Hence, 5 g enalapril maleate and 10 g urea dissolved in 25 mL of methanol were shaken in a calorimeter until equilibrium temperature was obtained.…”

Section: Determination Of the Minimum Ratio Of Rae And Nnae For The Fmentioning

confidence: 99%

“…Increments of 0.1 mL RAE were successively introduced into the calorimeter and the equilibrium temperature was recorded after each successive addition. A plot of temperature rise versus amount of RAE revealed the minimum amount of RAE utilized in the formation of co-inclusion compounds of enalapril maleate and RAE in urea (Zimmerschied et al 1949).…”

Section: Determination Of the Minimum Ratio Of Rae And Nnae For The Fmentioning

confidence: 99%

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Urea inclusion compounds of enalapril maleate for the improvement of pharmaceutical characteristics

Thakral

Мадан

2007

Journal of Pharmacy and Pharmacology

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Urea is a well known adductor for linear organic compounds. In the present study, enalapril maleate, a substituted cyclic organic compound, was successfully included in urea together with a suitable rapidly adductible endocyte (RAE). Formation of the urea inclusion compound was confirmed by Fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray diffraction. The modified Zimmerschied calorimetric method was used to estimate the minimum amount of RAE required for adduction of enalapril maleate in urea. Urea-enalapril maleate-RAE inclusion compounds containing varying proportions of guests were prepared and their thermal behaviour studied by differential scanning calorimetry. Regression analysis revealed an excellent r(2) value with regard to the influence of the relative proportion of RAE on the heat of decomposition. The inclusion compounds were found to exhibit good content uniformity and improved dissolution profile as demonstrated by increased dissolution efficiency. Studies revealed that urea inclusion may be a promising alternative for the formulation of potent poorly soluble drugs into immediate release products.

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Section: Minimum Ratio Of Rae and Nnae For Inclusion Of Nnae In Ureamentioning

confidence: 94%

Section: Determination Of the Minimum Ratio Of Rae And Nnae For The Fmentioning

confidence: 99%

Section: Determination Of the Minimum Ratio Of Rae And Nnae For The Fmentioning

confidence: 99%

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Urea inclusion compounds of enalapril maleate for the improvement of pharmaceutical characteristics

Thakral

Мадан

2007

Journal of Pharmacy and Pharmacology

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“…Their main importance consists in their use for isolating and purifying substances, especially hydrocarbons (10).…”

Section: Addition Compounds -Clathratesmentioning

confidence: 99%

Hydrocarbons

Večeřa¹,

Gasparič²

1971

Detection and Identification of Organic Compounds

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“…Zimmerschied, Dinerstein, Weitkamp, and Marschner (106) have reported that urea forms crystalline complexes with n-alkanes but not with branched and cyclic hydrocarbons. Zimmerschied, Dinerstein, Weitkamp, and Marschner (106) have reported that urea forms crystalline complexes with n-alkanes but not with branched and cyclic hydrocarbons.…”

Section: Industrial Applicationsmentioning

confidence: 99%

Crystallization.

Grove¹,

Gray²

1951

Ind. Eng. Chem.

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Few advances in theoretical correlation of crystallization phenomena have been reportedduring the past year. Emphasis has been placed on the effects of additions, as chemical ions, or physical treatments on both rate of crystallization and crystal habit. Much work has been reported on oriented growth of crystals on other crystalline or amorphous surfaces. A new field of application of crystallization has been opened up b y the use of crystalline complexes of urea and straight-chain hydrocarbons to separate straight-chain from branched and cyclic hydrocarbons. Processes for growing piezoelectric crystals have been improved. When ethylene glycol and ethyl alcohol are added to aqueous solutions of sodium sulfate, the deposition of solids on heating surfaces due to a lower solubility in water at higher temperature is avoided. theory and practice. It is stated that new nuclei may originate in situ in one or more of the following ways:1. By spontaneous n u c l e a t i o n from unseeded solution 2. By attrition of existing crystals 3. By mechanical impact 4. By formation of new crystals because of the inoculating influence of crystals already present 5. BY nucleation in restricting RYSTALLIZATION processes have continued to receive increased study and development. There have been c many investigations reported on the factors affecting the growth of crystals and the mechanisms involved in this growth. New techniques and improvements in industrial processes have been described. However, a satisfactory broad theoretical treatment of crystallization has not been reported. NUCLEATION AND RATE OF G R O W T HThe difficulty in formulating a complete theory describing the rates of formation of nuclei and growth of crystals is well expressed by Kirk and Othmer (47), who state:The mechanism of this process is very complex, as it involves the phenomena of diffusion, formation of nuclei, and crystal growth, all of which can take place a t the same time. No exact numerical calculations of the rates of any of these can be made at the present time so that, as a unit operation, crystallization is still highly empirfical in its methods. Because of this lack of any precise design calculations, the types of crystallizers have been numerous. To add to the designer's difficulty, it is frequently necessary t o produce crystals of a given shape, size, uniformity, and state of agglomeration as well as purity.However, the current status of crystallization theory and practice is summarized in some detail by these authors.Brown (IO) has pointed out that the problems concerning crystallization which are most frequently encountered deal with yields, purity, energy requirements, shape, size, and uniformity of the crystalline product, and rate of production of the desired crystals. Perry (61) has summarized in detail crystallization zones caked by local variations in th; concentration of the solution Umstatter and Hansen-Dannenitz (86) discuss the kinetics of precrystalline phases in liquids. They state that the inner friction of liquids is caused by ...

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Complexes of Urea with Linear Aliphatic Compounds

Cited by 32 publications

References 1 publication

Urea inclusion compounds of enalapril maleate for the improvement of pharmaceutical characteristics

Urea inclusion compounds of enalapril maleate for the improvement of pharmaceutical characteristics

Hydrocarbons

Crystallization.

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