George asks…
What does hydrogenation do to saturated fats vs unsaturated fats?
What causes hydrogenation? If natural saturated fats are subjected to high temperatures, will this make them hydrogenous? What if mono unsaturates such as olive oil are subjected to high heat, or polyunsaturated oils such as cottonseed oil? Is cottonseed oil made by heat or chemical processes?
admin answers:
Organic molecules consist mainly of carbon, hydrogen, and (often) oxygen atoms. Saturated fats refer to those fats whose molecules contain all the hydrogen atoms they can. Unsaturated fats contain some double bonds between some of the carbons instead. Hydrogenation breaks the double bonds, making two single bonds for each carbon; one of those will stay between the carbons, and the others will attach to hydrogen atoms supplied from some other substance. A very simple example would be ethane: H3C-CH3, which is saturated, and ethene: H2C=CH2, which is unsaturated. By breaking one of the two carbon-carbon bonds and substituting hydrogen atoms, the ethene will convert to ethane.
Others can add to this information to more fully answer your questions.
Maria asks…
What catalyst must be present in the hydrogenation of an alkene?
I keep getting different answers from different sources. Our teacher said platinum or palladium only MUST be present, but I sense she just meant those were two possible ones. Our book says nickel is an acceptable catalyst, and someone else told me that it has to be a heavy metal catalyst. Which is it? What defines a heavy metal and qualifies it to be a hydrogenation catalyst?
admin answers:
The most active would be Pt or Pd, but Ni could be used.
Industrially for small syntheses, Pt or Pd would be the catalyst of choice, but because of their expense, large scale e.g. Production of margarine is often using Ni
Sandy asks…
How does hydrogenation create trans fats?
My understanding is that hydrogenation adds hydrogen to double bonds. How can this create a trans bond if all trans bonds are double bonds? Are some bonds hydrogenated from CIS to saturated and then go back to a double bond as a TRANS?
admin answers:
The hydrogenation catalysts used also catalyze dehydrogenation reaction, and some of the dehydrogenation products are trans.
It is ironic that totally hydrogenated [ie, fully saturated] fats contain no trans fats, while the partially hydrogenated stuff, allegedly healthier, contains the trans fats.
Me, I use Canola oil….
I used to run part of a service lab where we did reactions under pressures up to 60,000 psi [though most were at 5,000 to 10,000 psi] or that had a potential to explode. One day one of the techs asked if “hydrogenated” oils were the same as the hydrogenations we did. I said they were, whereupon he looked nauseated and said he was never going to eat margarine again….
Sandra asks…
What is the difference between hydrolysis, hydrogenation, reduction and hydration?
I keep getting confused between these. So i know hydrogenation is used to remove double bonds and make margerine and stuff and you’re just adding Hydrogen but isn’t reduction also adding hydrogen (opposite of oxidation) and hydrolysis seems to be adding water to split up a molecule (eg acid hydrolysis of ester) but then hydration is like what?
HELP ME WHAT IS THE EXACT DIFFERENCE BETWEEN THEM
admin answers:
Hydrolysis: you break a bond with water
hydrogenation: you add more hydrogen to the molecule (it’s a reduction with H)
reduction: you reduce the oxidation state
hydration: you add a -OH group
Sharon asks…
What kind of compound is produced by the hydrogenation of an aldehyde or a ketone?
What kind of compound is produced by the hydrogenation of an aldehyde or a ketone?
A) Carboxylic acid
B) Alcohol
C) Alkane
D) Hemiacetal
E) Acetone
admin answers:
B) Alchohol
William asks…
Hydrogenation is the process of reacting hydrogen with vegetable oils to make them solidify. What is happenin?
Hydrogenation is the process of reacting hydrogen with vegetable oils to make them solidify. What is happening to the carbon-carbon bonds as the hydrogen is added
admin answers:
-HC=CH- + H2 –> -H2C-CH2-
unsaturated oil + H2 –> saturated fat
Ken asks…
How does Hydrogenation create Trans fats?
Hydrogenation removes triple & double bonds by adding hydrogens to the fat. But trans fats imply there are double bonds that have the trans isomer. So, chemically speaking, how is full or partial hydrogenation indicative of trans fats?
I am interested in either a detailed explanation of the chemistry behind this, or even the actual chemical reaction that clearly shows a trans fat as the product.
I’ve been looking all over, so thanks so much for your help!
admin answers:
Http://en.wikipedia.org/wiki/Trans_fat
hope this helps.
Joseph asks…
Hydrogenation of olive oil – moles of hydrogen produced from cyclohexene?
In the hydrogenation of olive oil, cyclohexene (MW = 82.15 gm/mol) is used as a source of hydrogens. How many moles of hydrogen are produced per mole of cyclohexene?
I have this question in a lab report, but there’s no balanced equation or anything. How do I solve this?
admin answers:
The reaction is called “catalytic transfer hydrogenation” or CTH. You should google that… Here’s one link
http://docs.google.com/viewer?a=v&q=cache:rYuxE2iey10J:www.erowid.org/archive/rhodium/pdf/cth.review.pdf+catalytic+transfer+hydrogenation+mechanism&hl=en&gl=us&pid=bl&srcid=ADGEESgRKwe1EHOd5dSvyY0SbE9sgBA-HL04haYExhUl4UCtfHPeqgK-r_-u-HfM13qM6zvk3ci6J6cE3urlP2CBwuyfKJwyTIVbcdywYOGOu9cLxT0FNOFatRRCM0oZNpKz0AjI2pR2&sig=AHIEtbROvA7seePsAkOh3ekdDFvQnWqPGA
but basically you’re removing H from cyclohexene. And di-enes are more reactive then alkenes. So after removing 2 H’s, the next 2 transfer easier… And what happens is this…
…HC – CH2
….//…….
HC…. ….CH2
…………/
H2C – CH2
goes to
…HC – CH
….//…….\
HC…. ….CH + H2
…………/
H2C – CH2
which continues on until you have benzene
…HC – CH
….//…….\
HC…. ….CH
…………/
..HC = CH
and that is stabilized by conjugated double bonds and delocalized electrons. Notice that cyclohexene has 10 H’s and benzene has 6? So that the cyclohexene has 4 available H’s to give up. Now usually, cyclohexene is in XS to speed up the rxn and increase the yield. I doubt you could extract further hydrogen for this process.
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