God
I know it's what your teacher may have taught you (I was taught that mild oxidation under 60˚C produces aldehydes in high school too), but this one of those really shameless lies taught in VCE chem. Acidified permanganate or dichromate is aqueous, and in aqueous solutions, aldehydes react with H2O to form geminal diols (an alcohol that has 2 hydroxyl groups attached to the same carbon). Hence you can't actually make a pure sample of aldehyde with the oxidising reagents you learned about in VCE, only its geminal diol (hydrate) form which has very different chemical properties from aldehydes

    I have trouble understanding hydrogen/carbon groups environments.
    I can identifying them, I just seem to get tripped up on whether different hydrogens are part of the same group.
    My common mistake is believing that two carbon environments are part of the same environment, when they are in reality different.

    For carbon/hydrogen sections to be a part of the same environment does the molecule HAVE to be symmetrical?

      Will

      If there is a H-environment identical to another in the molecule, then yes it's symmetrical. One hack I learned in uni for identifying whether or not 2 given environments are chemically equivalent is to pretend to cut off the C atom the H-environment is attached to from the rest of the molecule. You repeat it for the other environment (with a separate structure) and then you compare if the rest of the molecule is identical in both cases. If it is, then these 2 environments are equivalent (will post a visual example)

      • God likes this.

        There done, the squiggly line is just the convention we use in uni organic chem to represent a removed or arbitrary fragment.
        3-pentanone example

          Hi Billzene!

          Quick question:
          For the substitution reaction: Haloalkane + H2O(g) → Alcohol: NaOH / OH-

          Is water a gas? Or a liquid?

          Cheers!

          Btw: Absolutely love that method for h-environments! Maybe you should be called god, lol....

            God
            H2O isn't involved in the reaction converting haloalkanes to alcohols cuz it's uncharged and therefore a weak nucleophile. Unless you have a suitable catalyst, this reaction won't happen at a significant rate, that's why VCAA expects NaOH or KOH or OH-. You need OH- since converting a primary haloalkane into a primary alcohol is what we call an SN2 reaction, which requires a strong (charged) nucleophile. You may think OH- is the catalyst cuz it deprotonates water, but this isn't actually the case. You use up 1 particle of OH- to deprotonate 1 molecule H2O (making 1 particle of OH-) which then reacts with a haloalkane molecule (so you end up using 2 particles of OH- while only producing 1, for a net use of 1 OH- particle). Since catalysts by definition aren't consumed, OH- in this case is a reactant, not a catalyst

              Billzene So do you think we need to include states for the reactant and catalyst in hydration of alkenes. The 2020 report just says H20 / H+, but I usually see H2O(g) and H3PO4(aq). If the alkene and water are both gases, what is the acid aqueous in? Can things dissolve in steam? Thanks heaps Bilzene!

                  Also, in H-NMR, if the adjacent H on adjacent carbon atoms are in the same chemical environment (say a cycloalkane for example), is there any splitting pattern. If not, what about when the chemical environment is only slightly different, like for 2 adjacent CH2 groups in an octane molecule. Would it then be a splitting pattern with a tiny chemical shift either side?

                  And more importantly, does VCAA care? Thanks again.

                    Jesus
                    That's precisely the reason VCAA doesn't ask you the states of the H3PO4 catalyst since people can debate forever about whether it's (g) or (aq). You should always write H2O (g) though

                    Jesus
                    Hs in the same environment don't split each other, so for cyclohexane, you'll just see a singlet that integrates to 12

                    Slightly different chemical environments do produce splits. The width of the split doesn't matter since you only deal with 3J coupling in VCE chem

                          Does VCAA care if we do not specify something implied during naming of a compound?
                          Eg. Propanone is obviously propan-2-one

                            Will I'm pretty sure if you write something unnecessary like ethan-1-ol it will be marked wrong. But we will have to see what Bilzene says

                                Will
                                Great Question Will! I'm not sure, but would like to know was well 🙂

                                I wonder if it applies for the prefix as well (eg. "methyl ethanol"); Or would you need to write '1-methyl ethanol'....

                                Jesus Surely not... That'd be really mean of VCAA.....

                                    Will I'm sure Billzene will be able to give you a better answer since I'm a bit out of touch with VCE chemistry, but I am pretty sure that the numbers are not necessary for compounds that are implied. For example, no need to write propan-2-one, propanone will suffice (but you actually don't need to know how to name aldehydes and ketones for VCE chemistry anyway)

                                    Jesus
                                    You wouldn't lose marks for writing this.

                                        Will
                                        It's super inconsistent. I got a mark taken off on a SAC for writing propan-2-one due to the redundant number, but when I omitted it on my exam, I got a mark taken off there. This might be bad luck since the students I tutor never lost a mark on their exams for including or excluding a redundant position number.

                                          Hey Billzene,
                                          Do you know if we need to know which amino acids are essential?

                                            Will
                                            You absolutely don't. They'll tell you in the question if an amino acid is essential or non-essential

                                              13 days later

                                              hey
                                              for this questions write an equation that shows hso4- acting as base in water. Would it be. Thank you

                                              h2so4 + h20 = hso4- + h30+

                                                chemistry1111
                                                You’re showing H2SO4 acting as an acid, not HSO4- acting as a base. Remember that bases grab H+ i.e. they neutralise (remove) H3O+ instead of making more H3O+