Molecule structure formula of cyclopropane
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Cyclopropane

Cyclopropane is a cycloalkane molecule with the molecular formula C3H6 consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms. The bonds between the carbon atoms are a great deal weaker than in a typical carbon-carbon bond. This is the result of the 60° angle between the carbon atoms, which is far less than the normal angle of 109.5°. more...

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This ring strain has to be subtracted from the normal C-C bond energy, making the resultant compound more reactive than acyclic alkanes and other cycloalkanes such as cyclohexane and cyclopentane. This is the banana bond description of cycloalkanes.

However, cyclopropanes are more stable than a simple angle strain analysis would suggest. This is because the banana-bond model (without major tweaks) is incorrect; cyclopropane is better modeled as a three-center-bonded orbital combination of methylene carbenes. This results in the walsh orbital description of cyclopropane, where the C-C bonds have mostly pi character. This is also why cyclopropanes often have reactivity similar to alkenes. This is also why carbenes can easily add into alkenes to produce cyclopropanes.

Boiling point: -32.8°C Freezing point: -127°C

The naturally occurring pyrethrum insecticides (found in certain Chrysanthemum species) contain a cyclopropane ring.

Cyclopropane is an anaesthetic when inhaled, but has been superseded by other agents in modern anaesthetic practice. This is due to its extreme reactivity under normal conditions: when the gas is mixed with oxygen there is a significant risk of explosion.

Because of the strain in the carbon-carbon bonds of cyclopropane, the molecule has an enormous amount of potential energy. In pure form, it will break down to form linear alkanes and alkenes, including "normal", non-cyclic propane. This decomposition is potentially explosive, especially if the cyclopropane is liquified, pressurized, or contained within tanks. Explosions of cyclopropane and oxygen are even more powerful, because the energy released by the formation of normal propane is compounded by the energy released via the oxidation of the carbon and hydrogen present. At room temperature, sufficent volumes of liquified cyclopropane will self-detonate. To gaurd against this, the liquid is shipped in cylinders filled with tungsten wool, which prevents high-speed collisions between molecules and vastly improves stability. Pipes to carry cyclopropane must likewise be of small diameter, or else filled with unreactive metal or glass wool, to prevent explosions. Even if these precautions are followed, cyclopropane is dangerous to handle and manufacture, and is no longer used for anaesthesia.

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Military Medicine, Its Technology and Transition in the Mid-Twentieth Century
From Military Medicine, 4/1/04 by Connor, J T H

Military medicine and its technology were in transition during the Korean War era. The development of the army's Kolff-Brigham artificial kidney machine in the early 1950s, for example, introduced a generation of medical personnel to the benefits of dialysis both on and off the battlefield. Under the supervision of Dr. Paul Teschan of the Walter Reed Army Medical Hospital, this innovative piece of equipment worked "as well in a [Korean] rice paddy as it did in Washington." [1] Deploying helicopters to transport wounded soldiers heralded its more widespread use later under both military and civilian conditions. [2] But along with such equipment and ideas were tools and techniques employed in wars past.

A photograph of the operating room (OR) in a base hospital established during the Korean War captures continuity and change in military medicine of that time. Central is the patient-a North Korean soldier- who is undergoing emergency surgery. He is lying on the stretcher (little changed since Civil War days) that would have transported him to the OR, which in turn rests on some roughly cut 4"x4" wooden blocks. And, while surgical lamps are visible, the main source of illumination is a small ceiling light above the OR "table" which is tied in place with a bandage-a reminder that military surgery is often conducted under harsh and less than ideal conditions, with improvisation being the order of the day. Nonetheless, surgeons observe full aseptic precautions by wearing caps, masks, gloves, and gowns.

The patient, of course, is anesthetized. American military surgeons first experimented with inhalation anesthesia during the Mexican war of 1848-9 when ether was used, but this clinical practice was not fully implemented until the Civil War when chloroform became the anesthetic agent of choice. Close inspection of the photograph reveals how anesthetic technology during the Korean War bridged the old and the new methodology. To the left of the patient's head lie a facemask and tubing, both connected to a portable anesthesia apparatus. At least four types of equipment were employed in Korea, all of which were designed to deliver nitrous oxide, or possibly cyclopropane. The military use of these and other gases as anesthetic agents had begun by the end of World War I; their use would continue in the decades following until they supplanted almost all other methods.

An even more tried and true method is located to the bottom left of the photograph, where a metal canister containing Squibb's ether is clearly visible. To the right of it is a Schimmelbusch mask for the administration of both ether and chloroform; its invention dating back to the 1890s. The device consisted of a wire basket covered with gauze that was placed over the patient's mouth and nose. As the anesthetic agent was slowly dripped on to the gauze it evaporated, allowing the patient to inhale the vapor. The open-drop technique went back to the first days of anesthesia in the mid-1840s and it was employed somewhat during the early days of the Vietnam War, but the last extensive wartime use of this anesthetic method was in Korea.

The variety of anesthetic agents, equipment and delivery methods used during the Korean War reflected the lack of any official consensus or army policy pertaining to these issues. [3] During this era of transition, probably the greatest innovation within military medicine was not technological: the changed status of women in the Army Nurse Corps. Women had been associated with the army as nurses since the Civil War when the Surgeon General was authorized in 1861 to employ them, but they remained civilians regardless of the duties they performed. Almost 40 years later, at the outbreak of the Spanish-American War in 1898, the same situation prevailed even though over 1,500 women were contracted to serve. However, the Surgeon General established an Army Nurse Corps Division under the direction of a Washington, DC physician, Dr. Anita Newcomb McGee (1864-1940). In 1901, the Nurse Corps became permanent under the Medical Department. Although military personnel, army nurses were not commissioned but appointed for a series of three-year terms. Moreover, they did not carry rank until 1920-and even then they were only granted the status of an officer with relative rank. It would not be until 1947 that permanent commissioned officer status was established. [4] The two women officers pictured here-First Lieutenant Mary Keefe (far left) and Captain Cecilia Kirschling (second from the left)-were among the first cohort of the Army Nurse Corps to hold rank with the full privileges associated with it; their pay was also to be consistent with their rank for the first time. Kirschling's captain's bars are clearly visible on the right lapel of her uniform.

It is likely that either, if not both, of these officers also had specialized training in anesthesiology through the yearlong course begun in 1947 and offered at military sites such as the Walter Reed Army Medical Hospital. Nurse-anesthetists had been present at the operating table since World War I; they remained a prominent feature during World War II. In the Korean War, certified nurse-anesthetists were even more vital pursuant to a shortage of specialist physicians. Shortly after the end of the war, the U.S. Army established anesthesiology residency programs to address the shortfall of specialty-trained doctors. [5]

Sandwiched between World War II and the Vietnam War, the Korean conflict may well be one of America's forgotten wars for some. Yet, in addition to the political significance of this war, this era also shows how military medicine viewed from the perspectives of both technology and personnel was in transition much like the larger world.

Publisher's Note: These historical observations are provided pursuant to the current exhibition of the Armed Forces Institute of Pathology's National Museum of Health and Medicine, entitled Battlefield Surgery 101: From the Civil War to Vietnam. The museum is located on the grounds of the Walter Reed Army Medical Center, Washington, DC [www.nmhm.washingtondc.museum]

REFERENCES

1. McBride PT: Genesis of the Artificial Kidney. Deerfield, IL, Baxter Healthcare Corporation, 1987; 29-32. Connor JTH: Dutch Technological Migration and North American Commercial Exploitation: Dr. Willem Kolff and the Development of the Artificial Kidney in Hoefte R, Kardux JC, Connecting Cultures: The Netherlands in Five Centuries of Transatlantic Change. Amsterdam, VU University Press, 1994; 281-303.

2. Cowdrey AE: The Medic's War. Washington, DC, U.S Army Center of Military History, 1987.

3. Condon-Rall ME : A Brief History of Military Anesthesia in Zajtchuk R, Grande CM, Anesthesia and Perioperative Care of the Combat Casualty Washington, DC, Office of the Surgeon General, 1995; 882-3.

4. Feller CM, Moore CJ: Highlights in the History of the Army Nurse Corps.Washington, DC: U.S. Army Center of Military History, 1996.

5. Condon-Rall ME: Brief History of Military Anesthesia in Zajtchuk R,Grande CM, Anesthesia and Perioperative Care of the Combat Casualty Washington, DC, Office of the Surgeon General, 1995; 884.

J.T.H. Connor Ph.D., Assistant Director, National Museum of Health and Medicine, Armed Forces Institute of Pathology, Washington, DC

Copyright Association of Military Surgeons of the United States Apr 2004
Provided by ProQuest Information and Learning Company. All rights Reserved

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