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Ring strain results from a combination of angle strain, conformational strain or Pitzer strain (torsional eclipsing interactions), and transannular strain, also known as van der Waals strain or Prelog strain. The simplest examples of angle strain are small cycloalkanes such as cyclopropane and cyclobutane.
Structure of U-106305, a derivative of a cyclopropane fatty acid with six cyclopropane rings, isolated from Streptomyces sp. Although cyclopropanes are relatively rare in biochemistry, many cyclopropanation pathways have been identified in nature. The most common pathways involve ring closure reactions of carbocations in terpenoids.
Cyclopropane is the cycloalkane with the molecular formula (CH 2) 3, consisting of three methylene groups (CH 2) linked to each other to form a triangular ring. The small size of the ring creates substantial ring strain in the structure.
The small cycloalkanes – in particular, cyclopropane – have a lower stability due to Baeyer strain and ring strain. They react similarly to alkenes, though they do not react in electrophilic addition, but in nucleophilic aliphatic substitution. These reactions are ring-opening reactions or ring-cleavage reactions of alkyl cycloalkanes.
Mohler, John R., Dourine of horses – its cause and suppression (1911) Covering sickness, or dourine (French, from the Arabic darina, meaning mangy (said of a female camel), feminine of darin, meaning dirty), [1] is a disease of horses and other members of the family Equidae.
Because of the large ring strain energy of cyclopropanes (29.0 kcal per mole), they are often used as substrates for C-C activation through oxidative addition of a transition metal into one of the three C-C bonds leading to a metallacyclobutane intermediate. Substituents on the cyclopropane affect the course of its activation. [3]
Male horses are overall at a higher risk of catastrophic injury than female horses, with an overall odds ratio of 1.48. This does vary by study and country, including odds ratios of 1.12 in 1.61 in Australia, 1.76 in Canada, the United Kingdom, and 1.52–2.21 in the United States.
Additionally, horses with a hind limb lameness will tend to reduce the degree of leg use. To do so, some horses will reduce the contraction time of the gluteals on the side of the lame leg, leading to a "hip roll" or "hip dip" and appearance that the hip drops a greater degree on the side of the lame leg. [10]