Why does the solubility of fatty acids decrease as the double bonds decrease?
It doesn’t.Solubility of Oleic (C18:1) and Linoleic (C18:2) acids are almost the same.reference: https://www.jstage.jst.go.jp/art...For more details on fatty acids, please see…https://www.uio.no/studier/emner...
Why the double bond in unsaturated fatty acid chain cause bending?
I think it is cause by the strain energy of the double bond.
Why does solubility of fatty acids decreases as the length chain increases?
The longer the chain, the more hydrophobic carbons you’ve added. The more hydrophobic atoms you add, the less a molecule wants to dissolve in water. Shorter chains have the COOH groups that are hydrophilic to balance them out, but of course you can’t expect 2–3 COOH to cancel out 100 -CH2- ’s.
As carbon chain size increases, molecule become less and less water soluble. Why?
I'm gonna answer this question in the context of alcohols.The lower solubility of bigger alcoholsImagine what happens when you have got, say, 5 carbon atoms in each alcohol molecule.The hydrocarbon chains are forcing their way between water molecules and so breaking hydrogen bonds between those water molecules.The -OH end of the alcohol molecules can form new hydrogen bonds with water molecules, but the hydrocarbon "tail" doesn't form hydrogen bondsThat means that quite a lot of the original hydrogen bonds being broken aren't replaced by new ones.All you get in place of those original hydrogen bonds are van der Waals dispersion forces between the water and the hydrocarbon "tails". These attractions are much weaker. That means that you don't get enough energy back to compensate for the hydrogen bonds being broken. Even allowing for the increase in disorder, the process becomes less feasible.As the length of the alcohol increases, this situation just gets worse, and so the solubility falls.
How does a fatty acid molecule differ from a carbohydrate molecule?
A fatty acid molecule is a long chain carboxylic acid molecule. Either saturated with hydrogen bonds or containing unsaturated double bonds. Contain little Oxygen (only the carboxylic acid tail). No nitrogen. Hydrophobic, insoluble in water. Pic = http://biology.clc.uc.edu/courses/bio104/lipids.htm Carbohydrate literally means “hydrates of carbon.” and have the general formula: Cn(H2O)m. As such these molecules have greater hydrogen bonding capabilities and are usually hydrophilic (except some long chain polysaccharides) and soluble in water. Monosaccharide carbohydrates contain either Ketone or Aldehyde functional groups. No Nitrogen. pic = http://bioweb.wku.edu/courses/Biol114/Online/Carbo/carbo1.asp Amino acids all have the same base formula = alpha carbon bonded to an (nitrogen containing) amine group, a carboxylic acid group and a variable -R group. It is the variable R group which differentiates the amino acids. Because of the amine and carboxyl groups amino acids are usually fairly soluble in water. pic = http://www.chemicalconnection.org.uk/chemistry/topics/view.php?topic=5&headingno=3
How does the melting point of unsaturated fatty acid reacts with the increase in a double bond? Does it increase or decrease?
Generally, the melting point should increase with an increase in molecular weight - but that only happens in saturated fatty acids. These molecules can ‘stack' up in straight chains with greater intermolecular attractions which hold the compound together.The double bonds in unsaturated fatty acids cause kinks or bends to develop in the chain.The bends in the chains cause the molecular arrangement of fatty acids to be more disorganised than the straight-chain packing of saturated acids.That means that intermolecular forces are weaker and interrupted.The more double bonds, the more bends, the less intermolecular forces.So the melting point of unsaturated fatty acids decreases with an increase in the number of double bonds. It takes less energy to melt the compound.
Are saturated fats less soluble in water than unsaturated fats?
No.Fats consist of trigylicerides. Each triglycerides consists of one glycerol molecule coonnected to three fatty acids. (Visualise the letter ‘E’ except with longer horizontal lines, those represent the fatty acids).A fatty acid is a chain of carbon atoms with hydrogen atoms attached (visualise those above and below the horizontal line) and that chain has amethyl group on one end and an acid groop on the other end. Which is irrelevant to your question, but I want to give a full explanation.So back to the fatty acids. A mono unsaturated fatty acid ‘chooses’ in one spot to not bond with hydrogen, but instead double the bond between the carbon molecules. A polyunsaturated fatty acid ’chooses’ to not bond with hydrogen molecules in multiple spots. A saturated fatty acid bonds every carbon to 2 hydrogen items, the maximum.—-But, to come back to your question: this has no influence on solubility. Fats are all insoluble in water and this is because of nonpolarity. Hydrocarbon chains are nonpolar because of nonpolar bonds with hydrogen. Each fat has hydrocarbon chains and even though some are less saturated with hydrogen than others, they’re still hydrocarbon chains, it’s not enough to make a difference to have 1, 2 or 3 places in a fatty acid with no hydrogen atoms. Either something is soluble or insolubile (or soluble up to a certain percentage, but that’s not applicable here). You always have a triglyceride connected to 3 fatty acids and either the whole ’thing’ dissolves or it does not dissolve. In water, it just does not.http://www.chem.ucla.edu/~hardin...