Bazza's 3/4 chemistry questions

[WhoTookMyUsername]

1) whats the difference between ion ion bonding and ionic bonding
2) whats the equation for chloroethane -> ethylamine?
I thought you would just add NH3 with hydrochloride by product but answer says NH3 followed by NaOH
3) is it an OH- group or an OH group?
4) is it an +c=o group or a c=o group
5) how do you refer to " adjacent hydrogens " when talking about NMR? At the moment im saying, hydrogens in a different environment from the hydrogens resulting in the signal attached to adjacent carbon atms
6) what is a multiplet?
7)'does malic acid have 4 or 5 hydrogen environments?
when do you use atomic absorbtion spectroscopy  and uv vis spectroscopy
9)'what would you use to determine the ethanol content of a biofuel ( uv vis, aas or gas chromatog) and why? ( answer is gas chromat, not sure why)
10) what do youcall a  side group that consists of ch2oh?
11) what is the definition of a side group or side chain? ( is this the variable group on an amino acid?)
12) if a titre is involved in a calculation do you automatically go to 4 SF? I theres a 3 SF value ( thats what my teacher said, im not sure )
13) is it e- (aq) ? Or just e- and why ( redox)
14) what is a " peak" in high res nmr and how do you differnetiate between big peaks and small peaks  ( in your expression)


Thanks a lot

[IndefatigableLover]

2). Ethane + Hydrochloric Acid ---> Chloroethane
Chloroethane + Ammonia ---->Ethylamine + Hydrochloric Acid

Sorry couldn't help anymore...

[Hutchoo]

There's only a few I can answer with some confidence:
3) OH group.
4) c=o
7) Malic = 5.
AAS= Mostly used for metals [won't say always because I'm not 100% sure]. UV vis is used for organic compounds. 
10) hydroxymethyl group. [http://en.wikipedia.org/wiki/Hydroxymethyl]
13) e-, no states because a singular electron isn't considered as an atom//no states [that's how I think of it]

[pi]

3) -OH group, but OH is also accepted. It can't be OH- group as that would mean that the H has two bonds...

[charmanderp]

Alternatively just say hydroxyl group when appropriate, as that would be the answer the examiners would most appreciate.

[Mao]

1) whats the difference between ion ion bonding and ionic bonding Never heard of ion-ion bonding, as far as I can tell it's to describe an interaction between two ions, which is essentially the same as ionic bonding

2) whats the equation for chloroethane -> ethylamine? Amination is typically favoured by basic conditions, so I can understand why NaOH is used. NaOH has two functions, one as a catalyst, and another to scrap the HCl product. The latter function also helps with in terms of equilibrium considerations, but don't worry about that yet.
I thought you would just add NH3 with hydrochloride by product but answer says NH3 followed by NaOH

3) is it an OH- group or an OH group? OH group. There are no formal charges on the O, because it is meant to be covalently bonded to something else, thus neutral.

4) is it an +c=o group or a c=o group C=O group. Same argument as above.

5) how do you refer to " adjacent hydrogens " when talking about NMR? At the moment im saying, hydrogens in a different environment from the hydrogens resulting in the signal attached to adjacent carbon atms I do not understand this question. You can refer to adjacent hydrogens as adjacent hydrogens? e.g. 3 adjacent hydrogens split the signal into a quartet.

6) what is a multiplet? A complex peak that cannot be broken down into regular patterns, and thus cannot be formally identified, but nonetheless gives a ball-park indication of the hydrogen environments. This is usually the result of overlaps of several peak patterns.

7)'does malic acid have 4 or 5 hydrogen environments? Formally, 5 H environments. But the carboxyl group is very good at de-shielding the acidic H+, and so you'll find the two acidic H+ will most likely overlap. This is due to the finite precision of NMR instruments though. If we were to build the ideal instrument (i.e. instrument with infinite resolution and perfect precision, which is impossible), we will have 5 peaks, but in real instruments we will only see 4.

when do you use atomic absorbtion spectroscopy  and uv vis spectroscopy For organic coloured compounds, UV-vis. For metallic compounds, not so clear-cut. If we want to probe the elemental distribution, we will use AAS; AAS give us the elemental concentration, but not the chemical environments of those metal ions. If we want to look at particular structures around the metal ions (coordination complexes of metal compounds, you'll learn about this at uni), then we use UV-vis.

9)'what would you use to determine the ethanol content of a biofuel ( uv vis, aas or gas chromatog) and why? ( answer is gas chromat, not sure why) Ethanol is clear, so no UV-vis absorption. Ethanol doesn't contain metals, so not AAS. Ethanol is small and volatile, it fits the requirements of GC, and is very easily separated and analysed by GC.

10) what do youcall a  side group that consists of ch2oh? "Hydroxymethyl"

11) what is the definition of a side group or side chain? ( is this the variable group on an amino acid?) Side chains generally refer to branches which come off the 'backbone'. The backbone doesn't necessarily have to be all carbon (e.g. the protein backbone is a series of amide bonds, the DNA backbone contains phosphoester bonds). Not sure what you mean by 'variable group'.

12) if a titre is involved in a calculation do you automatically go to 4 SF? I theres a 3 SF value ( thats what my teacher said, im not sure ) No. Depends on the SF of the data

13) is it e- (aq) ? Or just e- and why ( redox) Free e- does not exist in condensed states. In fact, half reactions in redox don't actually take place, electron are not always particles, electron transfers are not particle transfers (more often they are smooth transition of the wavefunction/orbital/quantum-mechanics jazz). It is simply a formalization to make it easier to derive the chemical equation. e- is just e-.

14) what is a " peak" in high res nmr and how do you differnetiate between big peaks and small peaks  ( in your expression) What? a peak is a peak. Big peaks are bigger than small peaks. There isn't an arbitrary rule that says peaks bigger than a certain size are called 'big peaks'. Though in comparing peaks, both peak area and peak height should be considered.


Thanks a lot

[WhoTookMyUsername]

Thanks a ton everyone
With 5) i thought simply saying adjacent hydrogens might imply hydrogens attached to the same carbon as the one responsible for the peak

14) sorry badly written question. I mean how do you differentiate between big peaks ( 1 hydrogen environment ) and the peak splitting ( high res nmr ) when you  talk about them? Wuld you refer to big peaks as a " signal " and the split peaks as peaks? If so would you refer to low res nmr peaks as signals?

for determining the quantitiave ethanol content do you stillnhave to run standards of known ethanol concetnrations to determine the amount of ethanol present ( is area under peak relative or constant in gas chromatography)?

7) yesterday on a prac exam i wrote 5 environments, would you write this on the exam? ( if yes, are there general exceptions of overlap we need to know?)

2) i havent encountered the basic condition requirement for ehtanamine in my textbook, is this required knowledge? ( are we expected to write NaOH on exam?) ( are there other hidden catalysts like this for chemical pathways?)

Huge thanks

[sin0001]

For 10) wouldn't you always include the ch2oh in your carbon backbone when you're naming the carbons, instead of writing it as a side group?

[Mao]

With 5) i thought simply saying adjacent hydrogens might imply hydrogens attached to the same carbon as the one responsible for the peak That depends on the situation. Word it in a way that makes sense for that particular question

14) sorry badly written question. I mean how do you differentiate between big peaks ( 1 hydrogen environment ) and the peak splitting ( high res nmr ) when you  talk about them? Wuld you refer to big peaks as a " signal " and the split peaks as peaks? If so would you refer to low res nmr peaks as signals? You never have to refer to individual split peaks, as you will always be referring to the group (e.g. triplet, quartet, etc).

for determining the quantitiave ethanol content do you stillnhave to run standards of known ethanol concetnrations to determine the amount of ethanol present ( is area under peak relative or constant in gas chromatography)? Always run standards. For every method.

7) yesterday on a prac exam i wrote 5 environments, would you write this on the exam? ( if yes, are there general exceptions of overlap we need to know?) So long as you explain your reasoning, and your logic is correct, your answer should be accepted.

2) i havent encountered the basic condition requirement for ehtanamine in my textbook, is this required knowledge? ( are we expected to write NaOH on exam?) ( are there other hidden catalysts like this for chemical pathways?) If you think that piece of information is relevant to the question, then write it on the exam.

Key point here being, so long as your answer makes sense, they can't deduct marks. If you include extra information that are correct, they can't deduct marks. So at the end of the day, if your answers are scientifically correct, it doesn't matter if it is inside or outside of the course, you'll get the marks.

[WhoTookMyUsername]

thanks a lot Mao

Few more pre exam questions

1) what state do methyl esters exist in? (l,s, org?)
2) what state do long alcohols exist in ? (l, s, aq?)
3) what is the oxidation numbers of the elements in
 Cl207 (and why? i thought chlorine was always -1?)
5) what is a "fatty acid residue" and an "amino acid residue" (what does "residue" mean)
6) What is the "amino acid functional group" is it referring to the side chain or does it refer to carboxyl / amino?
7) If you split a dipeptide with HCL -> what is this called? (like, it would be hydrolysis if it was water)
what is Iodine number?
9) is it possible to produce 1-chloro-propanol from propene and chlorine gas (i don't think it is but one exam said it was :S)
10) what is the catalyst needed to chlorinate ethene (is it UV light? Is heat sufficient? not mentioned in textbook anywhere )
11) in chorlinating say ethane, the textbook says "heat or UV light" -> can you use heat? or does it have to be UV, which one is more correct?
12) When it says: "A" is titrated against "B" which one is in the burette? When "A" is titrated with "B" which one is in the burette?
13) Selenium dioxide (SeO2) is an important reagent in organic syntheses, as it is both an oxidant and a weak acid. In a certain reaction, 0.142 g of selenium dioxide reacted with exactly 25.52 ml of 0.100 M chromium (II) sulfate CrSo4 In the reaction Cr (2+) (aq) ions were oxidised to Cr (3+) (aq).
To what oxidation state was the Se4+ converted in this reaction? ( answers do something with ratios, but i haven't connected ratios with oxidation numbers in my mind)
14) can "butane" refer to 2-methylprop-ane
? (is chlorination of butene able to produce 1,2-dichloro-2-methylpropane?)


thanks a lot

[charmanderp]

thanks a lot Mao

Few more pre exam questions

1) what state do methyl esters exist in? (l,s, org?)
2) what state do long alcohols exist in ? (l, s, aq?)
3) what is the oxidation numbers of the elements in
 Cl207 (and why? i thought chlorine was always -1?)
5) what is a "fatty acid residue" and an "amino acid residue" (what does "residue" mean)
6) What is the "amino acid functional group" is it referring to the side chain or does it refer to carboxyl / amino?
7) If you split a dipeptide with HCL -> what is this called? (like, it would be hydrolysis if it was water)
what is Iodine number?
9) If your adding Cl2 across double bond would it typically produce
10) what is the catalyst needed to chlorinate ethene (is it UV light? Is heat sufficient? not mentioned in textbook anywhere )
11) in chorlinating say ethane, the textbook says "heat or UV light" -> can you use heat? or does it have to be UV, which one is more correct?
12) When it says: "A" is titrated against "B" which one is in the burette? When "A" is titrated with "B" which one is in the burette?
13) Selenium dioxide (SeO2) is an important reagent in organic syntheses, as it is both an oxidant and a weak acid. In a certain reaction, 0.142 g of selenium dioxide reacted with exactly 25.52 ml of 0.100 M chromium (II) sulfate CrSo4 In the reaction Cr (2+) (aq) ions were oxidised to Cr (3+) (aq).
To what oxidation state was the Se4+ converted in this reaction? ( answers do something with ratios, but i haven't connected ratios with oxidation numbers in my mind)
14) can "butane" refer to 2-methylprop-ene
? (is chlorination of butene able to produce 1,2-dichloro-2-methylpropane?)


thanks a lot

1) Liquid
2) Not exactly sure but I think nonanol and beyond are liquids
3) Oxygen is 7*-2=-14 so Cl2=+14 and Cl=+7. Look to oxygen and hydrogen to determine oxidation numbers of key elements rather than what is 'normal' or usual.
6) I've never actually heard that term before. The amino functional group and carboxyl functional group are separate entities AFAIK.
7) I think it's still hydrolysis, it just happens in the presence of hydrochloric acid (which happens in the stomach). But the resultant amino acids would be protonated.
Iodine number is the mass of iodine required to react with 100g of a lipid/oil/fatty acid. First work out the amount (in mole) of a certain fat/fatty acid in 100g and then calculate the number of double bonds in a fat/fatty acid. This becomes the ratio between the amount of iodine required and the amount of fat/fatty acid present. For example (from memory), arachidonic acid has 4 C=C double bonds, so four mole of Iodine is required for every one mole of acid. In a triglyceride containing arachidonic acid, you'd have 4*3 C=C double bonds, so 12 mole of Iodine would be required for every one mole of fat.
9) A Cl would be added to each carbon atom and there would be only a single bond between the carbons.
10) No catalyst is required (I believe it's because the positioning of the electrons in ethene leaves them exposed, because of the double bond, allowing the chlorine atoms to easily add themselves across, and hence a catalyst is not required).
11) Write 'hv' above the arrow, that's the symbol for light or energy.
12) Not completely sure because I'm pretty sure it could be either way. You have to deduce it from other parts of the question such as the word aliquot.
14) Butane refers only to the specific isomer which has four carbons in the longest chain. Otherwise you need to use the specific name, such as isobutane aka methylpropane. And 2-methylpropene has a different molecular formula anyway, so it's not even an isomer of butane. Just a heads up though, you don't actually need the 2 in front of methyl because the methyl group can only ever be on the second carbon atom!

[Shenz0r]

13) Selenium dioxide (SeO2) is an important reagent in organic syntheses, as it is both an oxidant and a weak acid. In a certain reaction, 0.142 g of selenium dioxide reacted with exactly 25.52 ml of 0.100 M chromium (II) sulfate CrSo4 In the reaction Cr (2+) (aq) ions were oxidised to Cr (3+) (aq).
To what oxidation state was the Se4+ converted in this reaction? ( answers do something with ratios, but i haven't connected ratios with oxidation numbers in my mind)

thanks a lot

From the information, you're given that Cr²⁺ ----> Cr³⁺ + e^-.
n(SeO₂) = 0.142/111 = 1.28 x 10^-3 mol
n(CrSO₄) = 0.02552 x 0.1 = 2.56 x 10^-3
n(CrSO₄) : n(SeO₂) = 2 : 1
Therefore, two electrons were donated from CrSO₄ to SeO₂.

The oxidation state of Se in SeO₂ is +4, and since it receives two electrons it is reduced to +2.

[pi]

2) Dodecanol and and beyond are solids I believe

[Mao]

1) what state do methyl esters exist in? (l,s, org?) Depends on how long the *oate chain is, but typically pure forms are liquids at room temperature

2) what state do long alcohols exist in ? (l, s, aq?) Depends on how long? At SLC, dodecanol and below (C12 and below) are liquids

3) what is the oxidation numbers of the elements in
 Cl207 (and why? i thought chlorine was always -1?) Not in presence of more electronegative compounds. the o.n. of Cl is +7 in this case. Consider the o.n. of atoms in: hydrogen peroxide (H2O2), and hypofluorous acid (HOF)

5) what is a "fatty acid residue" and an "amino acid residue" (what does "residue" mean) Residues refer to the 'functionalised' section of molecules of the same class. e.g. in amino acids, they all have the H2N-CH(Z)-COOH tail, so the rest of the molecule (the Z group or whatever you want to call it) is considered 'functionalised', as the different functions of different amino acids come from the different Z groups. Therefore, the Z group is the residue. Similar thing with fatty acids, the residue is the hydrocarbon part not including the carboxyl. Popular amongst biologists.

6) What is the "amino acid functional group" is it referring to the side chain or does it refer to carboxyl / amino? Never heard of this before. This could be referring to the 2-amino-1-carboxyl terminal group. Depends on the context.

7) If you split a dipeptide with HCL -> what is this called? (like, it would be hydrolysis if it was water) Firstly, HCL doesn't exist. If you hydrolyse (yes, it is also hydrolysis even though it's not water) the dipeptide with HCl, you will form an acyl chloride and an amine. Google for definition/pictures.

what is Iodine number? Google

9) is it possible to produce 1-chloro-propanol from propene and chlorine gas (i don't think it is but one exam said it was :S) What is the position of the hydroxy? Assuming you mean 1-chloro-2-propanol, you can do this with an addition reaction of propene + HOCl, see http://en.wikipedia.org/wiki/Hypochlorous_acid#Reaction_with_lipids

10) what is the catalyst needed to chlorinate ethene (is it UV light? Is heat sufficient? not mentioned in textbook anywhere ) Wikipedia says Lewis Acid, so ordinary acids or boron halides, though Lewis acids/bases are not part of the VCE course.

11) in chorlinating say ethane, the textbook says "heat or UV light" -> can you use heat? or does it have to be UV, which one is more correct? Has to be UV

13) Selenium dioxide (SeO2) is an important reagent in organic syntheses, as it is both an oxidant and a weak acid. In a certain reaction, 0.142 g of selenium dioxide reacted with exactly 25.52 ml of 0.100 M chromium (II) sulfate CrSo4 In the reaction Cr (2+) (aq) ions were oxidised to Cr (3+) (aq).
To what oxidation state was the Se4+ converted in this reaction? ( answers do something with ratios, but i haven't connected ratios with oxidation numbers in my mind) n(Cr2+)=0.00255mol from concentration, n(Se)=0.00128mol from mass, mole ratio is Cr:Se=2:1. In the reaction Cr2+ --> Cr3+ has 1 electron transfer, thus Se must uptake 2 electrons, therefore Se4+ --> Se2+

14) can "butane" refer to 2-methylprop-ane "2-methylprop-ane" doesn't exist. Generally butane refers to the linear butane, unless it is given as i-butane or isobutane, which is 2-methylpropane.
? (is chlorination of butene able to produce 1,2-dichloro-2-methylpropane?) only if it is isobutene

[WhoTookMyUsername]

Thanks for all the help, really appreciated guys
still have problems with the following questions

3) what is the oxidation numbers of the elements in
 Cl207 (and why? i thought chlorine was always -1?) Isn't chlorine more electronegative than oxygen? (if not, how can we tell? (as top right corner is most electronegative) was there a pneumonic... HNOF or something... or is that saying hydrogen bonds will form with nitrogen oxygen or flourine

5)
from IUPAC
http://old.iupac.org/goldbook/A00279.pdf
at the top it says amino acid residue is the whole AA?

does this mean referring to "amino acids" in a peptide molecule is incorrect? And what should we refer to the Z group as? Side chain, variable group?


thanks a lot

new question ->
1) on the data booklet , for 1-H NMR data there is an "R" group on many of the compounds -> can this be a lone hydrogen atom?
2) Question on MHS trial exam ->
(effectively) can C2H4Cl2 be produced from ethane and chlorine reacted and mixed in the presence of a catalyst?
(I put yes, but answer is no, not sure why)

4)
what is the difference between colorimetry an uv -vis?

thanks a lot