Here's 4 Alexander Donaldsons born to Alexander Donaldsons all born 1832 +/- 5 years. (from BVRs)
DONALDSON, Alexander Archibald
Gender:      Male
Birth Date:      14 Aug 1827
Birthplace:      Kirkcudbright, Kirkcudbright, Scotland
Recorded in:      Kirkcudbright, Kirkcudbright, Scotland
Father:   Alexander Christison DONALDSON
Mother:   Jane HOPE
Source:   FHL Film 1068032   Dates:   1743 – 1854
DONALDSON, Alexander
Gender:      Male
Birth Date:      10 Apr 1831
Birthplace:      Edinburgh Parish, Edinburgh, Midlothian, Scotland
Recorded in:      Edinburgh, Midlothian, Scotland
Father:   Alexander DONALDSON
Mother:   Janet SIMPSON
Source:   FHL Film 1066691   Dates:   1809 – 1855
DONALDSON, Alexander
Gender:      Male
Birth Date:      11 Jul 1832   
Christening Date:   5 Aug 1832
Recorded in:      Cupar, Fifeshire, Scotland
Father:   Alexander DONALDSON
Mother:   May LAMONT
Source:   FHL Film 1040101   Dates:   1778 – 1855
DONALDSON, Alexander
Gender:      Male
Birth Date:      6 Sep 1835
Birthplace:      Associate Congregation, Perth, Perth, Scotland
Recorded in:      Perth, Perthshire, Scotland
Collection:      Associate Session Congregation
Father:   Alexander DONALDSON
Mother:   Euphemia WILKIE
Source:   FHL Film 889486   Dates:   1743 - 1854
I hope one of these might be the one you're looking for. Good Luck!
Anne