Stankovic123's chem q's

[zvezda]

The question is, why does butanoic acid have a higher boiling point than butan-1-ol?
I would say the molecular has a higher molar mass, therefore more electrons and therefore stronger dispersion forces.
But i was thinking about it, and i was wondering whether the hydroxy group in the butanoic acid would be more polar than that of butan-1-ol?
would i be correct in saying this?
thanks in advance

[teletubbies_95]

HEYYY!:)
Great questions btw!
I dont know if this is right or not? Although butanol and butanoic acid both have hydrogen bonding ( intermolecular bonding) , but I'm guessing that the dipole -dipole attractions are much more stronger in the butanoic acid due to O double bond. Therefore having a greater boiling point.

[zvezda]

Hey, whats the deal with an iodine number? why not have a chlorine number or something like that?
this is just a question of curiosity more than anything

[zvezda]

Also, wouldnt a catalyst be required for the reaction between glycerol and a fatty acid to form a triglyceride? My textbook doesnt really mention anything.
cheers in advance

[Mao]

Hey, whats the deal with an iodine number? why not have a chlorine number or something like that?
this is just a question of curiosity more than anything

Iodine reacts much more readily. Plus, it is far less dangerous (Cl2 is very poisonous), heavier (therefore better for accuracy, logic is similar to choosing high Mw primary standards), and readily available as a solid (rather than Cl2 gas, which is dangerous and expensive to store).

Also, wouldnt a catalyst be required for the reaction between glycerol and a fatty acid to form a triglyceride? My textbook doesnt really mention anything.

Yes. But as with most biochemical reactions that take place in our body, the reaction is very complex and require a rather large number of enzymes. You can have a look at the reaction mechanism and the enzymes involved here: http://lipidlibrary.aocs.org/lipids/tag2/index.htm

[zvezda]

Iodine reacts much more readily. Plus, it is far less dangerous (Cl2 is very poisonous), heavier (therefore better for accuracy, logic is similar to choosing high Mw primary standards), and readily available as a solid (rather than Cl2 gas, which is dangerous and expensive to store).

Yes. But as with most biochemical reactions that take place in our body, the reaction is very complex and require a rather large number of enzymes. You can have a look at the reaction mechanism and the enzymes involved here: http://lipidlibrary.aocs.org/lipids/tag2/index.htm

Thanks Mao. Always appreciate your help

[zvezda]

Hey, when writing equations for the condensation reactions of carbohydrates, would it be necessary to refer to a catalyst?

[zvezda]

another question, with amino acids, why would a condensation reaction take place in preference to the -COOH donating an H+ to the -NH2??

[zvezda]

another question relating to the first one, wouldnt a catalyst be required for the condensation reaction of amino acids? heinemann doesnt mention anything. Does that just mean that it wouldnt be necessary to mention one if writing an equation for the reaction in response to, say, an exam question?

[zvezda]

Would anyone be able to explain why, when adding a basic or acidic solution to a solution containing zwitterions, the pH wouldnt drastically change. Ive been thinking about it for a while now, and I still dont see it.
thanks in advance

[zvezda]

How would you get an ionic bond in a tertiary structure protein between NH3+ and COO-? Why wouldnt the NH3+ just donate a proton to the COO-??

[Mao]

Would anyone be able to explain why, when adding a basic or acidic solution to a solution containing zwitterions, the pH wouldnt drastically change. Ive been thinking about it for a while now, and I still dont see it.
thanks in advance

Think buffers

How would you get an ionic bond in a tertiary structure protein between NH3+ and COO-? Why wouldnt the NH3+ just donate a proton to the COO-??

This comes from the inadequacy of VCE-level explanations (and indeed, most biochemistry explanations). The proton is actually 'shared' between the two groups, in the sense that the H makes two bonds (not quite as strong as covalent bonds, but similar).

[zvezda]

Think buffers
This comes from the inadequacy of VCE-level explanations (and indeed, most biochemistry explanations). The proton is actually 'shared' between the two groups, in the sense that the H makes two bonds (not quite as strong as covalent bonds, but similar).

Thanks Mao. that makes more sense, but I suppose I would just have to go with the "ionic bonding". I appreciate the help

[zvezda]

Hey,
In the Heinemann book, it says that "The bonds that determine the tertiary structure of the enzyme are altered as changes in the pH alter the ionisation of the amino acid residues in the protein". How is this so if the the amino acids have formed peptide links with other amino acids to form the protein in the first place? There would be no room for H+ donation?

[Ancora_Imparo]

Hey,
In the Heinemann book, it says that "The bonds that determine the tertiary structure of the enzyme are altered as changes in the pH alter the ionisation of the amino acid residues in the protein". How is this so if the the amino acids have formed peptide links with other amino acids to form the protein in the first place? There would be no room for H+ donation?

Don't forget the variable side groups (R groups) on each amino acid residue. Some of these contain carboxylic acid groups that can be deprotonated or amino groups that can be protonated depending on the pH. This will in turn have an effect on the ionic interactions between residues, thus potentially changing the tertiary structure of enzymes, or indeed any protein.