Skip to main content

Alkylhalides: Substitution reactions 5 (Sn1)


Alkylhalides: Substitution

Nucleophile substitution reaction (Sn1 reaction)

Solvent effects
To start off, have a look on the rate determing step of the Sn1 reaction, what happens with the compound becoming split into 2 ions:



The dielectric constant is a measure on how the solvent insulates the opposite charges from eachother. F.e. water will either contain the positive charged ion by using its partial negative oxygen, and it will contain the negative charged ion by using its partial positive hydrogen, thus separating both ions from eachother. A visual picture below from the Organic Chemistry book from Bruice found below to clear this up, on the left side the negative ion gets contained, on the right side the positive ion. 



Relative rates of water and ethanol solvents are the following:

100% water    1200

80% water / 20% ethanol   400
50% water / 50% water   60
100% ethanol   10


In the next blog post it will be the last one of the chapter of Substitution reactions, finally! 

Comments

Post a Comment

Popular posts from this blog

Alkylhalides: Substitution reactions 6 (Sn1)

Alkylhalides: Substitution Nucleophile substitution reaction ( Sn1 reaction ) Sn1 side reactions I will now discuss some side reactions that can occur when a Sn1 reaction takes place. Carbocation shift Illustrated in the scheme below: Benzyl- and allylhalides  Benzyl- and allylhalides can undergo Sn1 AND Sn2 reactions. How to distinct them? Sn1 conditions: protic solvent and by adding a weak attacking nucleophile. Note: Benzyl- and allylhalides easily undergo Sn1 reactions, because their carbocations are very stable. Sn2 conditions: aprotic solvent and by adding a strong attacking nucleophile. Note: tertiary benzylhalides and tertiary allylhalides will NOT undergo a Sn2 reaction because of the steric effects (see chapter Sn2 reaction blogposts). Sn2 reaction examples Sn1 reaction examples Sn1 and Sn2 reactions in biology, nature and medicines S-Adenosyl methionine This is a biological methylating agens, also known as SAM . It is a frequen...
1 comment
Read more

Alkynes: addition of H2 gas and Lindlar catalyst

Alkynes: addition of Hydrogen gas (H2) Performing a catalytic reduction on an alkyn will result in giving an alkane. The alkene intermediate will be formed in the process, but will immediately react into an alkane. The end result is just the formed alkane, without stacking of the alkene intermediate. The Lindlar catalyst In theory this is a "poisoned or defected" catalyst. If you use a normal catalyst you will get the above effect with your alkyne. The Lindlar catalyst contains Palladium combined with Calcium-carbonate and treated with Lead. Palladium is the actual catalyst, the calcium carbonate is the carrier of the substance and the lead is the poisonous compound. Using the Lindlar catalyst instead of another catalyst together with Hydrogen gas, will lead into forming the cis-alkene intermediate instead of the forming of the corresponding alkane. 
Post a Comment
Read more

Erythropoietin: definition, structure, synthesis in vivo

Definition: EPO: = erythropoietin   A glycoprotein hormon-like structure, a sialoglycoprotein, which is an important factor in the survival, growth and proliferation of erythroid precursor cells (EPC) and it improves the de novo creation, differentation and growth of red blood cells (RBC). Thus, EPO controls the erythropoiesis = production of RBC. EPC: these are cells that are located in the bone marrow, will eventually form the RBC. RBC: cells responsible for the transport and distribution of oxygen throughout the body. Structure: Built out of 165 aminoacids (AA). They are all connected and form 1 polypeptide chain.  Although, within the chain, there are 2 disulfide bonds.  Respectively on positions: Cys7-161 and Cys29-33  Cys = cystein and the numbers indicate the positions these AA are located. Cystein structure. Available  sulfide  group for bonding There are also 4 positions where there is a possibility for glycosylation  Namel...
Post a Comment
Read more