Random Question Thread.

[d0minicz]

hey i'm having a bit of trouble with 1-H NMR (high res) and 13-C NMR
how do you guys approach a question based on those? need desperate help

thansk ...

[Dark Horse]

High Res Proton NMR
1) How many different chemical environments?
2) How many lines is it divided into? (eg. sextet) Out of curiosiy what is the term for the lines which a peak is divided into?
3) Are the atoms in question adjacent to an electronegative atom? If so, higher chemical shift value.
4)What r the chemical shift values? use data booklet to compare. (isnt exaclty same as data booklet)
4) Use knowledge to determine structural formula of molecule
Thats a basic rundown, but changes from question to question

Carbon NMR is just counting how many different Carbon environments, then using data booklet to determine what they are.

Hope it helps

[TrueTears]

dom check here : http://vcenotes.com/forum/index.php/topic,9769.30.html

check kj_'s reply. I think that is pretty thorough.

[d0minicz]

When 50 mL of 0.2 M HCl and 50 mL of 0.2 M Ba(OH)2 are mixed, waht will the pH of the resulting solution be?
thanks

[TrueTears]

first can you write the acid - base reaction for this?

Next n(HCl) = 0.05 * 0.2

n(Ba(OH)2) = 0.05*0.2

find which is in excess by using mole ratios from the equation you wrote.

whichever is in excess find the amount unreacted by using the original minus the amount reacted.

From this work out the concentration of H+

then pH = -log([H+])

[d0minicz]

Hey i need verification to what the oxidation of lipids involves thanks

[d0minicz]

Is there any diff between 6-methyl, 3-chloroheptane and 3-chloro,6-methylheptane

[chem-nerd]

Is there any diff between 6-methyl, 3-chloroheptane and 3-chloro,6-methylheptane

whether there is any difference isn't your main issue - it should be 5-chloro-2-methylheptane

[d0minicz]

dont functional groups come first :S

[TrueTears]

chloro begins with c methyl begins with m, must have c before m.

[d0minicz]

so they definately take a mark off for the wrong order ?

[ed_saifa]

The higher the atomic number, the higher the priority.
H, CH3, NH2, OH, SH,Cl,Br,I

[Mao]

Is there any diff between 6-methyl, 3-chloroheptane and 3-chloro,6-methylheptane

not exactly, but it should be 2-methyl-5-chloroheptane

[chem-nerd]

this is from the 08 assessors report


6aii.
Either of: • 5–chloro–2–methylheptane
             • 3-chloro-6-methylheptane
Common errors in part ii. included identifying the compound as hexane rather than a heptane and the use of ‘septane’ rather than heptane.

Responses to part ii. revealed how difficult it can be to achieve consistency in systematic naming of some compounds, with an almost even split between 5–chloro–2–methylheptane and 3–chloro–6–methylheptane responses.

The interpretation of systematic nomenclature rules tends to be influenced to a significant degree by the focus on functional groups in this course. Giving the chloro– functional group precedence leads to 3–chloro–6–methylheptane. Alternatively, treating the alkyl– and chloro– groups as having equal prominence leads to numbering the carbon chain from the end nearest a substituent group, which in this case will be from the end nearest the substituent methyl group, which is then located on C–2 and the chloro– group on C–5, leading to 5–chloro–2–methylheptane. Both approaches are reasonable at this level.

Students should remember that substituent groups should be listed in alphabetical order.

[d0minicz]

4.65g of metal X formed an oxide with an emperical formula of XO3 ,and a mass of 8.94g. What is the relative atomic mass of the metal X?
thanks
edit: i mean ; do we just assume 1:1 ratio? need help on that