Betty asks…
Why does the FDA allow hydrogenation in foods when companies are advertising no trans fat?
I have seen several products with 0 grams of trans fat on the package. I turn it around to the ingredients and it contains partially hydrogenated oils, which is the same as trans fat.
admin answers:
Hydrogenation of fats removes or reduces both ‘trans’ and ‘cis’ fatty acids by replacing double bonds (the cause of the trans and cis conformation) with H atoms – single bonds result
Thomas asks…
Can hydrogenation using a Pd/C catalyst reduce a ketone to a methylene group?
I tried using this reducing agent on a ketone on my o-chem test. Apparently it doesn’t work and I got the question wrong. But I think it is right. Could anyone provide references?
admin answers:
Reduction with H2 forms the alcohol which will not further reduce. Look at the Wolff Kishner reaction or the Clemmenson Reduction for CH2 formation
Mandy asks…
Why are alkenes more reactive to hydrogenation than ketones?
Also, why are cis alkenes more reactive than trans alkenes? This is a catalysis question, any help appreciated!
admin answers:
The C=C double bond is not as strong as the C=O double bond so it is easier to reduce.
Richard asks…
Biochemistry: How does partial hydrogenation effect corn oil?
A label on a container of margarine states that it contains partially hydrogenated corn oil. How has the corn oil been changed?
admin answers:
Corn oil is normally polyunsaturated. Oils with most of their acids as polyunsaturates are liquid, even at low temperatures. To turn the product into a malleable solid, it is partially hydrogenated, so that there are many fewer double bonds in the product. (But some still remain so the product is not a solid at body temperature or baking or whatever the desired mix is).
Chemical forms of hydrogenation tend to create both isomeric forms of the double bonds, both cis- and trans-. This is the main process by which trans- fatty acids are formed. Enzymatic formation of the bonds would place them in only the cis- form.
Susan asks…
What is the benefit of hydrogenation in foods?
I’m aware of the negative effects, but there must be some benefit to the companies… why do they hydrogenate product components?
admin answers:
Hydrogenated oils extend product shelf life. This is why homemade goods go stale/spoil quickly.
Laura asks…
A compound with the formula C5H6 takes up 2 moles of hydroge on catalytic hydrogenation. Give one possible?
A compound with the formula C5H6 takes up 2 moles of hydroge on catalytic hydrogenation. Give one possible structure that would fit the information given.
admin answers:
C5H6 + 2 H2 —> C5H10
So how about this…
……..CH2
……/….
…CH….CH
….||…….||….
…CH – CH
reacting with 2 H2 to form…
……..CH2
……/…..
…CH2…CH2
….|………|….
…CH2 – CH2
Daniel asks…
why are catalysts used in a hydrogenation reaction?
to be more specific, how do they speed up the hydrogen-carbon bonding?
(PS- I thought double bonds were easier to break than single bonds)
thank you.
I mean, hydrogenation reactions are relatively slow and catalyst is added to lower the activation energy…..
but since double bonds are easier to break than single bond…why does hydrogenation process take a long time?
is it because the electronegativity of Hs and Cs the very similar?
admin answers:
Catalysts work by lowering the transition state energy needed for the reaction to proceed.
There are a number of ways they work; sometimes the electron orbitals of the metal interact with the electron orbitals of the double bond, and also orient the hydrogen atoms to add to the double bond.
But regardless, the energy necessary for the reaction to proceed is lowered.
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