A level_OCR_Chemistry_Marking Scheme 1_2020 | SPS F108 12.1_Carbonyl Compounds, Carboxylic Acids, Esters & Polyesters

Document Content and Description Below

SPS F108 12.1_Carbonyl Compounds, Carboxylic Acids, Esters & Polyesters_A level_OCR_Chemistry_Marking Scheme 1 Carbonyl Compounds, Carboxylic Acids, Esters & Polyesters Mark Scheme 1 Level A L... evel Exam Board OCR Sub-Topic Time Allowed: 86 minutes Score: /71 Percentage: /100 Grade Boundaries: A* A B C D E U >85% 77.5% 70% 62.5% 57.5% 45% <45% Question Answer Mark Guidance 1 (a) (Relative) solubility (in stationary phase)  1 ALLOW how well the compound dissolves IGNORE retention time AND partition DO NOT ALLOW adsorption OR absorption (b) (i) Compound B AND M+/molecular ion peak (at m/z) = 124  1 ALLOW Mr = 124 IGNORE compound B because m/z = 124 ALLOW C7H8O + = 124 OR C7H8O2 = 124 2 ALLOW peak at (m/z =) 109 due to HOC6H4O+ ALLOW peak at (m/z =) 109 due to loss of CH3 IGNORE reference to other peaks in the spectrum (ii) Compound (B) is less soluble in the stationary phase/ liquid 1 ORA Answer refers to the first compound to emerge from the column ALLOW compound (B) is more soluble in mobile phase/gas ALLOW compound interacts less with stationary phase/liquid OR compound interacts more with mobile phase/gas IGNORE compound adsorbs less IGNORE compound is not very soluble (comparison needed) IGNORE volatility OR reactivity Question Answer Mark Guidance (c) (i) reagent = K2Cr2O7 AND H2SO4  compound C =  ester =  3 ALLOW acidified dichromate ALLOW H+/any acid IGNORE concentration of acid ALLOW Na2Cr2O7 /Cr2O 2- /(potassium OR sodium) 7 dichromate((VI)) - ALLOW acidified MnO4 ALLOW Tollens’ reagent/ammoniacal silver nitrate IGNORE conditions ALLOW correct structural OR displayed OR skeletal formulae OR a combination of above as long as unambiguous ALLOW ECF from incorrect compound C Check positions of OH groups ALLOW esterification of phenol group Question Answer Mark Guidance (ii) curly arrow from H– to Cδ+  dipole AND curly arrow from C=O bond to O  correct intermediate AND curly arrow to H+  3 ANNOTATE ANSWER WITH TICKS AND CROSSES ETC curly arrow must come from lone pair on H or negative charge on H curly arrow must come from the bond, not the carbon atom curly arrow must come from lone pair on O or negative charge on O and go to H or positive charge on H Where circles have been placed round charges, this is for clarity only and does not indicate a requirement ALLOW correct structural OR displayed OR skeletal formulae OR a combination of above as long as unambiguous ALLOW for second stage IF H2O is used it MUST show the curly arrow from the negative charge or lone pair on the oxygen atom of the intermediate to H in H2O AND from the O—H bond to the O in H2O. Dipole not required on water molecule Penalise missing –OH on intermediate only IGNORE product – already given credit in part (i) - - - - [Show More]

Last updated: 1 year ago

Preview 1 out of 38 pages