Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Cycloalkane shopping experience:
1. Compare - without doubt the biggest advantage that the Cycloalkane offers shoppers today is the ability to compare thousands of Cycloalkane at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Cycloalkane? Wrong! If the Cycloalkane is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Cycloalkane then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Cycloalkane? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Cycloalkane and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Cycloalkane wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Cycloalkane then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Cycloalkane site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Cycloalkane, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Cycloalkane, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
image:cyclobutane.png
Cycloalkanes (also called naphthenes) are chemicals with one or more carbon rings to which
hydrogen atoms are attached according to the formula CnH2n. Cycloalkanes with a single ring are named analogously to their normal
alkane counterpart of the same carbon count:
cyclopropane,
cyclobutane,
cyclopentane, cyclohexane, etc. The larger cycloalkanes, with greater than 20 carbon atoms are typically called cycloparaffins.
Cycloalkanes are classified into small, normal and bigger cycloalkanes, where cyclopropane and cyclobutane are the small ones, cyclopentane, cyclohexane, cycloheptane are the normal ones, and the rest are the bigger ones.
Nomenclature
See also: IUPAC nomenclature
]The naming of polycyclic alkanes such as ] alkanes and
spiro compound alkanes is more complex, with the base name indicating the number of carbons in the ring system, a prefix indicating the number of rings (eg, "bicyclo"), and a numeric prefix before that indicating the number of carbons in each part of each ring, exclusive of vertices. For instance, a bicyclooctane which consists of a six-member ring and a four member ring, which share two adjacent carbon atoms which form a shared edge, is -bicyclooctane. That part of the six-member ring, exclusive of the shared edge has 4 carbons. That part of the four-member ring, exclusive of the shared edge, has 2 carbons. The edge itself, exclusive of the two vertices that define it, has 0 carbons.
The group of cycloalkanes are also known as
naphthenes, as they are compounds of
petroleum or naphtha.
Properties
Cycloalkanes are similar to alkanes in their general physical properties, but they have higher
boiling point, melting point, and density than alkanes. This is due to stronger
London forces because the ring shape allows for a larger area of contact. Cycloalkanes exhibit almost the same degree of unreactivity as alkanes, due to only containing unreactive C-C and C-H bonds; however, the ring strain (see below) can cause cycloalkanes to be more reactive.
Ring strain
The carbon atoms in cycloalkanes are
sp3
orbital hybridization and therefore a deviation from the ideal tetrahedral bond angles of 109.47 degrees causes an increase in potential energy and an overall destabilizing effect. Eclipsing of hydrogen atoms is an important destabilizing effect as well. The
strain energy of a cycloalkane is the theoretical increase in energy caused by the compound's geometry, and is calculated by comparing the experimental
standard enthalpy change of combustion of the cycloalkane with the value calculated using
average bond energies.
Ring strain is highest for cyclopropane, in which the carbon atoms form a triangle and therefore have 60 degree C-C-C bond angles. There are also three pairs of eclipsed hydrogens. The ring strain is calculated to be around 120 kJ/mol. Cyclobutane has the carbon atoms in a puckered square with approximately 90 degree bond angles; by "puckering" it reduces the eclipsing interactions between hydrogen atoms. Its ring strain is slightly less, at around 110 kJ/mol. For a theoretical planar cyclopentane the C-C-C bond angles would be 108 degrees, very close to the tetrahedral angle. Actual cyclopentane molecules are puckered but this only changes the bond angles slightly so that angle strain is relatively small. The eclipsing interactions are also reduced, leaving a ring strain of about 25 kJ/mol.
In cyclohexane the ring strain and eclipsing interactions are negligible because the puckering of the ring allows ideal tetrahedral bond angles to be achieved. As well, in the most stable
chair form of cyclohexane, axial hydrogens on adjacent carbon atoms are pointed in opposite directions, virtually eliminating eclipsing strain.
After cyclohexane, the molecules are unable to take a structure with no ring strain, resulting in an increase in strain energy, which peaks at 9 carbons (around 50 kJ/mol). After that, strain energy slowly decreases until 12 carbon atoms, where it drops significantly; at 14 another significant drop occurs and the strain is on a level comparable with 10 kJ/mol. After 14 carbon atoms, sources disagree on what happens to ring strain, some indicating that it increases steadily, others saying that it disappears entirely.
Reactions
The simple and the bigger cycloalkanes are very stable, like
alkanes, and their reactions for example
radical substitution, are like alkanes.
The small cycloalkanes - particularly cyclopropane - have a lower stability due to
Baeyer strain theory and
ring strain. They react similarly to alkenes, though they don't react in
electrophilic addition but in nucleophilic aliphatic substitution. These reactions are ring opening reactions or ring cleavage reactions of
alkyl cycloalkanes. Cycloalkanes can be formed in a Diels-Alder reaction followed by a
catalytic hydrogenation.
References
External Links
image:cyclobutane.png
Cycloalkanes (also called naphthenes) are chemicals with one or more
carbon rings to which hydrogen atoms are attached according to the formula CnH2n. Cycloalkanes with a single ring are named analogously to their normal alkane counterpart of the same carbon count: cyclopropane,
cyclobutane,
cyclopentane,
cyclohexane, etc. The larger cycloalkanes, with greater than 20 carbon atoms are typically called cycloparaffins.
Cycloalkanes are classified into small, normal and bigger cycloalkanes, where cyclopropane and cyclobutane are the small ones, cyclopentane, cyclohexane, cycloheptane are the normal ones, and the rest are the bigger ones.
Nomenclature
See also: IUPAC nomenclature
]The naming of polycyclic alkanes such as ] alkanes and
spiro compound alkanes is more complex, with the base name indicating the number of carbons in the ring system, a prefix indicating the number of rings (eg, "bicyclo"), and a numeric prefix before that indicating the number of carbons in each part of each ring, exclusive of vertices. For instance, a bicyclooctane which consists of a six-member ring and a four member ring, which share two adjacent carbon atoms which form a shared edge, is -bicyclooctane. That part of the six-member ring, exclusive of the shared edge has 4 carbons. That part of the four-member ring, exclusive of the shared edge, has 2 carbons. The edge itself, exclusive of the two vertices that define it, has 0 carbons.
The group of cycloalkanes are also known as
naphthenes, as they are compounds of
petroleum or naphtha.
Properties
Cycloalkanes are similar to alkanes in their general physical properties, but they have higher boiling point,
melting point, and density than alkanes. This is due to stronger
London forces because the ring shape allows for a larger area of contact. Cycloalkanes exhibit almost the same degree of unreactivity as alkanes, due to only containing unreactive C-C and C-H bonds; however, the ring strain (see below) can cause cycloalkanes to be more reactive.
Ring strain
The carbon atoms in cycloalkanes are
sp3 orbital hybridization and therefore a deviation from the ideal tetrahedral bond angles of 109.47 degrees causes an increase in potential energy and an overall destabilizing effect. Eclipsing of hydrogen atoms is an important destabilizing effect as well. The
strain energy of a cycloalkane is the theoretical increase in energy caused by the compound's geometry, and is calculated by comparing the experimental standard enthalpy change of combustion of the cycloalkane with the value calculated using
average bond energies.
Ring strain is highest for cyclopropane, in which the carbon atoms form a triangle and therefore have 60 degree C-C-C bond angles. There are also three pairs of eclipsed hydrogens. The ring strain is calculated to be around 120 kJ/mol.
Cyclobutane has the carbon atoms in a puckered square with approximately 90 degree bond angles; by "puckering" it reduces the eclipsing interactions between hydrogen atoms. Its ring strain is slightly less, at around 110 kJ/mol. For a theoretical planar cyclopentane the C-C-C bond angles would be 108 degrees, very close to the tetrahedral angle. Actual cyclopentane molecules are puckered but this only changes the bond angles slightly so that angle strain is relatively small. The eclipsing interactions are also reduced, leaving a ring strain of about 25 kJ/mol.
In
cyclohexane the ring strain and eclipsing interactions are negligible because the puckering of the ring allows ideal tetrahedral bond angles to be achieved. As well, in the most stable
chair form of cyclohexane, axial hydrogens on adjacent carbon atoms are pointed in opposite directions, virtually eliminating eclipsing strain.
After cyclohexane, the molecules are unable to take a structure with no ring strain, resulting in an increase in strain energy, which peaks at 9 carbons (around 50 kJ/mol). After that, strain energy slowly decreases until 12 carbon atoms, where it drops significantly; at 14 another significant drop occurs and the strain is on a level comparable with 10 kJ/mol. After 14 carbon atoms, sources disagree on what happens to ring strain, some indicating that it increases steadily, others saying that it disappears entirely.
Reactions
The simple and the bigger cycloalkanes are very stable, like
alkanes, and their reactions for example
radical substitution, are like alkanes.
The small cycloalkanes - particularly cyclopropane - have a lower stability due to
Baeyer strain theory and
ring strain. They react similarly to alkenes, though they don't react in electrophilic addition but in nucleophilic aliphatic substitution. These reactions are ring opening reactions or ring cleavage reactions of
alkyl cycloalkanes. Cycloalkanes can be formed in a
Diels-Alder reaction followed by a catalytic hydrogenation.
References
External Links
- "Cycloalkanes" at the online Encyclopædia Britannica
- "Cycloalkanes" by the Chemistry staff at Westminster College, Pennsylvania
Cycloalkane - Wikipedia, the free encyclopedia
Cycloalkanes (also called naphthenes, especially if from petroleum sources) are types of alkanes which have one or more rings of carbon atoms in the chemical structure of their ...
Category:Cycloalkane - ChemSemWiki
This page was last modified 17:18, 6 March 2007. This page has been accessed 265 times. Privacy policy; About ChemSemWiki; Disclaimers
cycloalkane - Wiktionary
Definition from Wiktionary, a free dictionary
cycloalkane - definition of cycloalkane by the Free Online Dictionary ...
cy·clo·al·kane (s kl-l k n) n. An alicyclic hydrocarbon with a saturated ring. Also called cycloparaffin. cycloalkane (s kl-l k n) Any of various cyclic saturated ...
Alkyl cycloalkane - Wikipedia, the free encyclopedia
Alkyl cycloalkanes are chemical compounds with an alkyl group with a single ring of carbons to which hydrogens are attached according to the formula
Cycloalkane – Wikipedia
Die Cycloalkane (Cyclane, ältere Bezeichnung: Naphthene, Cycloparaffine) sind eine Stoffgruppe von ringförmigen, gesättigten Kohlenwasserstoffen.
Cycloalkane Conformations - EMOC
Educational Materials for Organic Chemistry Cycloalkane Conformations. The following molecules will require the Chime plugin for viewing and rotating.
Index of Cycloalkane Conformations - EMOC
Educational Materials for Organic Chemistry Cycloalkane Conformations. Pages accessed through this index will require the Chime plugin for viewing and rotating the molecular models ...
cycloalkane. The American Heritage® Dictionary of the English ...
cycloalkane. The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
CycloAlkane Nomenclature
1) parent name Hexane 2) cyclo 3) subsitutents or ethyl,methy, propyl 4c) 4-ethyl-2methyl-1propylcyclohexane or is it 1 ethyl 3 methyl 4 propylcyclohexane
