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Adding some more points to Tarins first statement....

1) One 180 rotation in plane gives the same molecule.

2)Two 180 rotations out of plane gives the same molecule...

Refer to the attached pics...

A,B,C,D,E,F,G,H are all the same...

(once u assign the priorities,u can check their configuration (R,S) to confirm that)

In such case ,

should be much more appropriate !!!

"If a reaction is carried out in a protic solvent, whose molecules have a hydrogen bonded to an oxygen or to a nitrogen, the larger atom is a better nucleophile in an SN2 reaction."

A protic solvent usually consists of R-O-H or N-H groups.
They form hydrogen bonding with the hydrogen atom of the nucleophiles.

An SN2 reaction requires that the nucleophile attacks the carbon atom.

Hence the nucleophile should be free from the solvant molecules which solvate it(by forming hydrogen bonding)

Now less the size of the anion, more easily it is solvated, as it can appear more close to it and form stronger hydrogen bonds.
Hence in case of small anions in polar protic solvents, it requires that more energy is provided to it to strip off the solvent molecules forming the Hydrogen bond with it.This reduces the strengt hof the nucleophile.

In case of polar aprotic solvents there is no solvation of the anions hence it follows the usual trend "a strong base is a better nucleophile"

Organic Doubt,based on SN2 reaction

inspiring as always! :)

It can be easily judged by eliminating the possibilities.

A simple rule to remember

Base gives elimination

Nucleophile gives substitution

1)Temperature:All elimination reactions are thermodynamically controlled (it is because u convert a stable compound to an unstable 1...like frm alkanes to alkenes)

2)Kinetics:All substitution reactions are kinetically controlled

3)Strength of base or nucleophile:A strong base or nucleohile gives 2nd order reactions as it attacks the carbon atom or abstracts a proton before the molecule can ionize

4)Stearic effects:Primary halides undergo 2nd order reactions as their carbocations are not stable..they usually undergo SN2 if the nuclophile is strong and E2 if the base is strong (stronger than the leaving group, as it makes the leaving group a weak base n thus a stable conjugate base n thus makes it a good leaving group)

Teritiary halides + Weak base = SN1 (SN2 is not possible as back attack is not possible due to the stearic hindrance)

Teritiary halides + Weak base+heat = SN1+E1 (SN2 is not possible as back attack is not possible due to the stearic hindrance)

Teritiary halides +Strong base=E2 (E1 not possible as a strong base gives a second order reaction)

5)Reactions with secondary halides=Mixture of products (they follow the rule bse=elimination, nuc=substitution)

6)Stearic effects on nucleophile:A bulky nucleophile cannot attack a carbon atom but can easily abstract a proton, hence bulky nucleophiles give elimination products

7)Solvent effects:good ionizing solvent or polar protic solvent gives 1st order reactions n vice versa...

(others can add some more points)

It is the common name of Aluminium oxide.

chem formula-

similar to

http://www.goiit.com/posts/list/physical-chemistry-atomic-structure-32905.htm#166225

http://www.goiit.com/posts/list/0/institutes-and-material-for-those-who-need-peter-sykes-n-other-61604.htm

For those who need Peter Sykes n othr related study material

cool! :)

Apple seeds contain cyanogenic acids in small amounts....eating too many of them results in poisoning

yup....RyuAmakusa is right...frame of reference should be mentioned.