TYS questions on Organic Chem

bonkysleuth SG

Below shows some information about a homogolous series of carbon compounds called esters.

CH3OCH3 methoxymethane

CH3OC2H5 methoxyethane

CH3OC3H7 methoxypropane

CH3OC4H9 methoxybutane

The ethers are saturated compounds . (this statement is marked as 'false'.)

How do I know they are not saturated compounds?

2. Olive oil contains oleic acid. Oleic acid is an unsaturated acid which has the molecular formula C17H31CO2H . How many carbon-carbon double bonds are present in 1 molecule of oleic acid?

Have totally no idea how to go about doing this. Please guide me along. Thank you.

SBS n SMRT SG

Below shows some information about a homogolous series of carbon compounds called esters.

CH3OCH3 methoxymethane

CH3OC2H5 methoxyethane

CH3OC3H7 methoxypropane

CH3OC4H9 methoxybutane

The ethers are saturated compounds . (this statement is marked as 'false'.)

How do I know they are not saturated compounds?

2. Olive oil contains oleic acid. Oleic acid is an unsaturated acid which has the molecular formula C17H31CO2H . How many carbon-carbon double bonds are present in 1 molecule of oleic acid?

Have totally no idea how to go about doing this. Please guide me along. Thank you.

1. Esters may have a oxygen-carbon bond that may be broken, thus, they are not satuarted.

2. write out the entire structural formulae, check the number of H bonds with C, and each C should have 4 bonds, so if there is not enough H, those C will have double bonds, remember COOH as functional gp, write this out first before others,......

dkcx SG

2. Olive oil contains oleic acid. Oleic acid is an unsaturated acid which has the molecular formula C17H31CO2H . How many carbon-carbon double bonds are present in 1 molecule of oleic acid?

Have totally no idea how to go about doing this. Please guide me along. Thank you.

Excluding the COOH group, C17 will have 1CH3 and 16 CH2 total requiring 35H, since there are only 31H, there must be 4 double bonds.

bonkysleuth SG

1. Esters may have a oxygen-carbon bond that may be broken, thus, they are not satuarted.

But then again, these are ethers... not esters as what you had written. ;p

bonkysleuth SG

Anyway, 3 more questions from the TYS.

1. In the polymerisation of ethene to form poly(ethene), there is no change in

A boiling boint

B density

C mass

D molecular formula

2. Which natural resources is being depleted by the manufacture of plastcs?

I know it is fossil fuel but can someone explain to me the direct link between plastics and depletion of fossil fuel? Is it because petroleum (a type of fossil fuel) is being used to produce naptha, etc. And the propane in naptha is used to produce ethene which is then polymerised to get poly(ethene)?

3.Which statement is true about ethanol?

A it is formed by the catalytic addition of steam to ethene

B It reacts with ethyl ethanoate to form an acid

I wrote the answer as A, but the printed answer is B. Is the answer wrong?

thanks

dkcx SG

Anyway, 3 more questions from the TYS.

1. In the polymerisation of ethene to form poly(ethene), there is no change in

A boiling boint

B density

C mass

D molecular formula

2. Which natural resources is being depleted by the manufacture of plastcs?

3.Which statement is true about ethanol?

A it is formed by the catalytic addition of steam to ethene

B It reacts with ethyl ethanoate to form an acid

I wrote the answer as A, but the printed answer is B. Is the answer wrong?

thanks

Not 100% sure but

1) Density

2) Petroleum is the source of all hydrocarbons such as ethene, propene etc which is the monomer for some of the most common polymers. They can also be obtained by cracking of the higher C hydrocarbons to yield the smaller 1s for polymerisation.

3) The answer could be correct.The reaction is an electrophilic addition, not sure what catalytic addition means unless it means addition by use of a catalyst...

I know that an ester will react with an acid to give the alcohol but i'm not sure whether it can work by reacting with the alcohol to give the acid but it might be possible.

d3sT1nY SG

Anyway, 3 more questions from the TYS.

1. In the polymerisation of ethene to form poly(ethene), there is no change in

A boiling boint

B density

C mass

D molecular formula

2. Which natural resources is being depleted by the manufacture of plastcs?

3.Which statement is true about ethanol?

A it is formed by the catalytic addition of steam to ethene

B It reacts with ethyl ethanoate to form an acid

I wrote the answer as A, but the printed answer is B. Is the answer wrong?

thanks

1) Mass? Because the volume changes (Gas->Solid), that's why density changes.

3) Ethene + Steam: Electrophilic Addition due to the high density of electrons at the double bond region. Catalytic addition, H3PO4 as the catalyst?

Not sure why the answer is B though.

UltimaOnline SG

>>> Ethanol reacts with ethyl ethanoate to form an acid <<<

That's false, of course. There's no reaction between ethanol (alcohol) and ethyl ethanoate (ester).

To obtain ethanoic acid from the ester, you have to use base-promoted hydrolysis followed by protonation/acidification, or simply use acid-catalyzed hydrolysis to obtain the carboxylic acid directly.

Reduction of the ester (using lithium aluminium hydride in dry ether, followed by protonation/hydrolysis) generates ethanol (2 moles of ethanol from 1 mole of ethyl ethanoate).