Don't be so hard on yourselves.
Don’t forget, organic chemistry help can be found at organic chemistry help
I love this, it is the largest test bank on the web for organic chemistry exams. It is completely free and is a great way to study for your exams. Testbank is located at organic chemistry, scroll to the middle of the page and click on “practice exams”. There are over 50 practice tests from Organic I and Organic II, most with the correct answers. See former exams from universities around the country.
Good luck and happy reacting.
Hey Everybody, cruising the net again I found that AceOrganicChem.com has launched their latest product, 200 Organic II Audio Flashcards. With audio flash cards, you not only see the answer, but hear an explanation of it too. I purchased the to take a test run for my students and I love it. Some people are visual learners, some are audio learners. This helps both!!
To see a video demonstration, go to organic chemistry flashcards.
To purchase, go to organic chemistry.
Thanks, and as always, happy reacting.
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Let’s face facts: alkanes don’t have many uses. In real life, they are non-polar solvents, larger-chaines ones can be used to make wax, and they are good for burning/they make good fuels. As far as organic chemistry goes, alkanes are very boring. They have only three uses in your class:
1) Solvents: Alkanes are very good non-polar solvents. See tip #XX for more information on this.
2) Halogenation: Alkanes can be reacted with bromine or chlorine under free-radical conditions to obtain an alkyl halide. See tip #XX for more information on this.
3) Combustion: This is the fuel part. Complete combustion is an alkane reaction with oxygen to obtain CO2 and water, as shown in the following example: C3H8 +5O2 à 3CO2 + 4H2O + Heat
There is only a small possibility that you will see a combustion reaction on one of your exams. Therefore, the only real uses for alkanes in your undergraduate organic chemistry class will be as a solvent or in a halogenation reaction. Hence, if you have an alkane in one of your exam reactions, it should be very simple to determine its role. If there is a halogen (usually either Br2 or Cl2) , then beware of a halogenation reaction. Otherwise, it is most likely safe to say that if you have an alkane in your reaction, it is a solvent and does not participate as a reactant.
For more helpful organic chemistry information, please go to organic chemistry.
Today’s site of the week is www.chemicalforums.com. I have been a part of this site for a while, and have been pretty impressed with it so far. Once you register, you can post chemistry questions for the experts to answer. The experts are extremely knowledgable, and you get a bunch of responses in a very short time. Great resource for the undergrad who wants a quick answer to a topic that has eluded them to this point. An even better resource for the grad student who wants to run a research idea by a 10,000 lb brainiac.
This site gets 4.5 beakers out of 5.
For further information on this, please see organic chemistry.
During the election cycle, there was much discussion about our energy future. I imagine that it clear to most that we can not continue to live on Middle Eastern oil forever, but what are the options? Clean coal technology? Wind? Solar? Nuclear? Natural Gas? The choices are numerous and complex. Further, and maybe more importantly, we must consider the impact on the environment.
For those of you living in the great state of Texas, you have options. One of them is Texas Electricity. You have the choice to save on commercial electric, business electric and residential electric by switching to deregulated electric supply at Texas Electric Company.
What impresses me is the ability to save the environment, with numerous “green” electric options. Clean, renewable energy options will keep greenhouse gases like CO2 from being placed in our atmosphere and lead to a measurable decrease in global warming over the coming year. You can do your part to help with that by visiting Texas Electricity.
Pollution free electricity is clean, affordable and reliable power. you can learn more about this and other options for your residential and business power needs by visiting Texas Electricity. Remeber, this is our chance to leave the Earth better for our children than we found it.
This is important throughout organic chemistry, but will be especially important when trying to determine the products of elimination and substitution (E1, E2, SN1, SN2)reactions. There are generally three trends to remember when discussing how nucleophilic a reactant is:
1) Size - Generally, the more linear and/or smaller the nucleophile, the more nucleophilic it will be. This is because it can react at more sites and will not be sterically hindered if it is smaller or linear.
2) Electronegativity- The more electronegative an atom is, the less nucleophilic it will be. This is because more electronegative atoms will hold electron density closer, and therefore will be less likely to let that electron density participate in a reaction. We see this in calculations and experiments that show nucleophilicity decreases as you get closer to fluorine on the periodic table (C > N > O > F)
3) Polarizability- The more polarizable an atom is, the more nucleophilic it will be. Polarizability is defined as the ability to distort the electron cloud of an atom, which allows it interact with a reaction site more easily. Generally, polarizability increases as you travel down a column of the periodic table (I > Br > Cl > F)
Below is a table of relative nucleophilic strength. This is relative because nucleophilic strength is also dependant on other factors in the reaction, such as solvent.
|
VERY Good nucleophiles |
HS-, I-, RS- |
|
Good nucleophiles |
Br-, HO-, RO-, CN-, N3- |
|
Fair nucleophiles |
NH3, Cl-, F-, RCO2- |
|
Weak nucleophiles |
H2O, ROH |
|
VERY weak nucleophiles |
RCO2H |
As shown above, as a general rule, the anion of a reactant will be a better nucleophile than the neutral form. (i.e. RCO2- is a better nucleophile than RCO2H)
For more information on this and other topics of organic chemistry interest, please visit organic chemistry
Structures of molecules can be difficult to piece together at first when you are just starting in an organic chemistry class. One of the tricks that can greatly help with this is to know the uncharged or “normal” state for atoms that are commonly found in organic molecules. Here is a table of the most common of those:
– C has four bonds and no lone pairs
– N has three bonds and one lone pair
– Halogens (F, Cl, Br, I) have one bond and three lone pairs.
– O has two bonds and two lone pairs
– H has one bond and no lone pairs
Three more rules:
- C, N, O are central atoms, meaning that they will always be in the middle of your molecule.
- H and halogens are terminal atoms, meaning that they will only have one bond and be at the ends of molecules.
- With the exception of H, atoms in group I & group II are only counterions (+1 or +2 and not involved in resonance).
Remember, these rules are for when the atom is uncharged; this does not apply to charged atoms. For example, a carbocation (a positively charged carbon atom) will have only three bonds with no lone pairs while a carbanion (a negatively charged carbon atom) wlll have three bonds with one lone pair.
Notice that all of these atoms still follow the octet rule. However, beware of atoms that do not follow the octet rule, as phosphorus is an example of an atom that can have more than an octet of electrons. Shown below is triphenylphosphine oxide, a byproduct of the Wittig reaction.
Elements with open d-subshells, like phosphorous and sulfur, do not always follow the octet rule. More examples of this are SF6 and PCl5. However, carbon, nitrogen and oxygen will follow the octet rule.
A problem we see students constantly running into is that they do not readily recognize strong acids. This is a terrible mistake and should never happen. You will need to quickly recognize strong acids and which atom they will be protonating. As far as strong acids go, you should immediately recognize the Magnificent Seven:
STRONG ACIDS: HI, HCl, HBr, HNO3, H2SO4, HClO3, H3PO4
Just think that that it’s the three hydrogen halides and the four acids that have N, S, Cl, and P as central atoms. Many students remember the other four acids with the mnemonic, something you would never say to a girlfriend: “Never Say ‘Please Clean’ ”.
Once you have recognized that you have a strong acid present in your reaction, it is necessary to determine what it is protonating. Remember that H+ is electron-deficient (Lewis acidic) and will look for an electron-rich (Lewis basic) atom to protonate. This could be a nitrogen atom, such as an amine, or an oxygen atom in a carbonyl or an alcohol. Most often, the atom being protonated will have a lone pair somewhere.
Take Home Message: Know the strong acids, the mnemonic Never Say ‘Please Clean’ might help
